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GINNERS

DBi

• _

PRESENTED

THE UNIVERSITY OF TORONTO

Examination copies of the accompany-
ing Book have just reached us from the
Publishers. We have pleasure in sending-
one to your address.

THE COPP, CLARK COMPANY, LIMITED

9 Front St. West, TORONTO

BOTANY FOR BEGINNERS

BOTANY

BEGINNERS

ERNEST EVANS

NATURAL SCIENCE MASTER, MECHANICS' INSTITUTE
AND TECHNICAL SCHOOLS, BURNLEY

Hontion

I iff

MACMILLAN AND CO., LIMITED

NEW YORK : THE MACMILLAN COMPANY
1899

RICHARD CLAY AND SONS, LIMITED,
LONDON AND BUNGAY.

PREFACE

IT is now generally accepted by educationists that experi-
mental work is an essential part of instruction in any branch of
physical or natural science. Too much importance cannot be
attached to knowledge gained direct from Nature ; and it is
gratifying to know that many questions now set by public
examining bodies are designed to test the student's own obser-
vations and experience. As an instance of this, it is worth
pointing out that in the syllabus for Botany, published by the
Department of Science and Art, the examiners remark : —

" The examination will be especially directed towards ascer-
taining the amount and character of the practically acquired
knowledge possessed by the students."

To provide students with a means of obtaining such know-
ledge, this little work has been prepared in the spirit of the
foregoing remarks, as a guide to beginners in the practical study
of plants. The attempt is often made to study Botany without
the practical examination of plants, and it has produced on the
popular mind an impression that the subject is uninteresting.
This is the result of the old method of teaching Botany by
means of ideals or definitions ; the new method is to examine
the plants from as many points of view as possible, and to draw
conclusions from actual observations. Studied in this way,
the subject becomes one of living interest, instead of being
merely a collection of technical names and terms. It is with
the idea of placing in the hands of all who are interested in the
study of plants a book which shall be a guide and companion
during a first course that the present volume has been prepared.

PREFACE

Though the book has been primarily designed to cover the
syllabus of the Department of Science and Art, it is by no means
a " cram-book " for that particular examination, and a thorough
knowledge of its contents will not only lay the foundation for
further work, but should enable a student to pass any elementary
examination in Botany with distinction. The book should also
be useful to teachers in elementary schools, in assisting them to
prepare object lessons with plants for the instruction of their
pupils.

Teachers are recommended to see that the students perform
the experiments, and keep a complete record of the results
obtained. Most of the plants necessary for the experiments can
be easily obtained ; the others can be grown in the school
grounds. A small collection of fruits, seeds, dried and mounted
plants, should be kept in all schools.

It is hoped that the introduction into this book of a series of
carefully graded experiments with simple apparatus will prove
useful to many students and teachers, and will be the means of
making botanical science a more popular subject in the future
than it has been in the past.

Many of the illustrations have been prepared, after careful
consideration, by my friend and colleague Mr. W. E. Holt, to
whose skill I am much indebted. Figures 128 to 131 have been
drawn by my former student, Mr. H. Wright, A.R.C.S. The
figures marked S. have, by the kindness of the publishers, been
placed at my disposal from Strasburger's Text Book of Botany.

The questions at the ends of the chapters will serve to test
whether students have clear ideas on the subjects dealt with.
Those with years indicated are from papers set at the Science
and Art Department's examinations ; and T. signifies Training
College questions.

In conclusion, I desire to acknowledge my indebtedness to
Prof. R. A. Gregory and Mr. A. T. Simmons, B.Sc., for many
valuable suggestions and much help during the preparation of
the manuscript, and the passage of the work through the press.

ERNEST EVANS.

MECHANICS' INSTITUTE AND TECHNICAL
SCHOOLS, BURNLEY.

CONTENTS

CHAPTER I

INTRODUCTION .......... ,

CHAPTER II

MORPHOLOGY— STUDY OF THE BODY OF A PLANT

CHAPTER III

ANATOMY — STUDY OF THE SHOOT 1 6

CHAPTER IV
THE STUDY OF THE SHOOT (continued) 34

CHAPTER V

ANATOMY — STUDY OF ROOTS 51

CHAPTER VI

SECTIONS, HOW TO PREPARE AND EXAMINE THEM 6l

CHAPTER VII

THE HISTOLOGY OF THE CELL 74

CHAPTER VIII

THE HISTOLOGY OF THE TISSUES 92

CHAPTER IX

THE HISTOLOGY OF THE SHOOT AND ROOT 103

CONTENTS

CHAPTER X

PAGE
THE PHYSIOLOGY OF NUTRITION Il6

CHAPTER XI

THE ABSORPTION AND MOVEMENT OF WATER IN THE PLANT 137

CHAPTER XII

THE PHYSIOLOGY OF GROWTH AND MOVEMENT 152

CHAPTER XIII

TLOWER AND INFLORESCENCES 164

CHAPTER XIV

THE TERMS USED IN DESCRIBING THE FLOWER 178

CHAPTER XV

THE DEVELOPMENT AND MORPHOLOGY OF THE FLOWER . .

CHAPTER XVI

POLLINATION AND FERTILISATION .

CHAPTER XVII

THE MORPHOLOGY OF SEED AND FRUITS, AND THEIR DISTRI-
BUTION 222

CHAPTER XVIII

THE PHYSIOLOGY OF REPRODUCTION " . V . .' . . 237

CHAPTER XIX

THE CLASSIFICATION OF PLANTS . . 242 I

CHAPTER XX

CLASSIFICATION OF PLANTS (contimied} 265 j

CHAPTER XXI

PLANT DESCRIPTION ".''.. .."".' .' .' . V . . 283:

INDEX . ........ 287;))

BOTANY FOR BEGINNERS

CHAPTER I

INTRODUCTION

Definition. — The branch of science the object of which is
the study of the plant, from- as many different points of view
as possible, is termed Botany. All its laws can be proved by
observation and experiment, and it is consequently known as
one of the concrete sciences. If we wish to include all plants
it is impossible to clearly define what is meant by a plant,
because the higher plants differ in many respects from the
lower, and so many exceptions to any rule we may state present
themselves. It is true that in olden times our forefathers
divided all forms of life into animals and plants, but we find
we cannot, with the knowledge of to-day, draw a clear boundary
line between them. It is easy to recognise the difference
between an oak tree and a horse, but when the lower forms of
life are examined no clear division can be drawn between
animals and plants. All living things are built up of the same
kind of material, vfz. — protoplasm. Protoplasm has been
called the physical basis of life, because life is never found apart
from it. There appears to be no difference between the
protoplasm obtained from animals and that obtained from plants.
In fact, what we speak of as the tree of life is forked, the
animals being found on one side and the plants on the other,
.-IB B

BOTANY FOR BEGINNERS CHAP.

and both of them spring from the lowly forms which are found
at the base.

Higher Animals. Higher Plants.

E.g. Horse. E.g. Oak.

Lower forms
of life.

Living and Non-living Bodies.— It will be well to at
once consider the question of the differences between living and
non-living bodies ; and here a fairly clear boundary line can be
drawn.

1. Living bodies are characterised by the nature of their
external form. Their shape is definite, and bounded more or
less by curved surfaces. Non-living bodies are either
amorphous, that is without shape ; or crystalline, that is bodies
with a definite shape. Crystals are bounded by flat surfaces
meeting in sharp edges.

2. Living bodies are able to reproduce their kind, but non-
living bodies have not this power of reproduction.

3. Living bodies take in food, which supplies material for
growth, the growth taking place from the inside. Non-living
bodies cannot take in food, but tjiey can increase in size if
placed under suitable conditions. The growth or increase in
size of a crystal always takes place on the outside, not
internally like the growth of either animals or plants.

The Object of the Plant.— Plants, then, are living things,
and we must learn to treat them as such. Plants produce
seeds, but not, as the reason is sometimes stated, for the use of
man, but so that the continuity of the particular race of plants
can be kept up. The living, working, struggling plant, has only

INTRODUCTION

one object in life, that is, to reproduce its kind. All the parts
of the plant are designed with this object in view ; the shape,
colour, and perfume of the flowers, and all the various contriv-

FIG. i. — Illustration of the difference in the external forms of the mineral,
vegetable, and animal kingdoms.

ances with which plants are endowed, are to be regarded as
means towards accomplishing this reproduction.

Scope of Our Lessons. — We shall have to consider the
plant from the following points of view : — (i) Morphology, or the
science of form and structure ; (ii) Physiology, or the science of
function j (iii) Classification, or the science of relationship.

B 2

.BOTANY FOR BEGINNERS CHAP.

Morphology. — That portion of the study of living things
which deals with the shape and structure of the various organs
of plants or animals is termed morphology. Morphology is
divided into anatomy, which means, as far as our lessons are
concerned, the structure of the plant to the extent it can be
made out by the aid of a knife, the naked eye, or by the aid of
a simple lens ; and histology, or the minute structure of the
various organs which require the use of the compound micro-
scope for their complete study.

Physiology. — This division of botany is concerned with
those functions which, taken together, constitute the life of the
plant. Just as morphology is concerned with what plants are,
so "physiology deals with what they do. There are several
divisions into which physiology can be divided, for example : —

1. The Physiology of Nutrition, or how a plant obtains its
food, together with the changes that go on in the food due to
the activity of the living substance of the plant, so that the food
may become part of it, or become converted into sugar, starch,
cellulose, and proteids.

2. The Physiology of Movement, or how plants move. That
various parts of plants can move is shown by the opening and
closing of flowers, the so-called sleep of leaves, and the changes
in the position of stems, such as the twining stems of the hop,
and the tendrils of the vine. This department of physiology
tries to answer all questions relating to the causes that produce
the various movements of plants, and how these movements
are affected by the action of light, heat, and moisture.

3. The Physiology of Reproduction, or how plants reproduce
" their kind. Some plants reproduce by means of bulbs and

tubers. This kind of reproduction is termed vegetative,
because the parts of the plant that enter into the process are
only portions produced by the vegetative functions of the plant.
In far the greater number of cases, plants reproduce their
kind by means of seeds. This kind of reproduction is termed
7 sexual.

Classification. — The province of classification is to point
out the relationship between different plants. Many methods
of classification have been devised, and many of them are known
as artificial systems.

One of the best known is that of Linnaeus, which is based on

INTRODUCTION

the number and arrangement of the parts of the flower. All
the various artificial systems have been superseded by that
called the Natural System, which is based on the resem-
blances and differences of plants. The natural system ot
classifying plants is the most perfect yet used, though it is not
up to the present complete, because the relationships between
different plants have not been fully worked out.

To make the above divisions of our subject yet more clear to
the reader we arrange them in a tabular form, which should be
carefully learnt.

Botany.

I J

Morphology. Classification. Physiology.

I I

Anatomy. Histology.

Nutrition. Movement. Reproduction.

Life-History of a Plant.— Every plant possesses what is
termed a life-history, that is, its life has a beginning, it passes
through certain stages, old age comes on, and at last it dies.
All the changes that a plant undergoes from birth to death make
up its life-history. In all the higher plants the life-history com-
mences with the germination of the seed, continues as that of
the seedling, is prolonged as the plant becomes mature, then
flowering takes place, seeds are produced, the parent dies, and
the continuity of the race is kept up by the young plant in the
seed.

Necessity for Practical Work.— Having now given some
idea of the scope and aims of botany, and the boundary lines
which mark off the different divisions of the subject, the
importance of practical work must next be insisted on.

No true knowledge of natural history can be obtained without
practical work ; and there is no doubt that such work is well
adapted for cultivating the powers of observation and attention
to details, attainments which are likely to prove of value in
whatever walk of life the student may afterward find himself.

Botany is one of the best subjects with which to commence
the study of science, because the necessary materials for

BOTANY FOR BEGINNERS

CHAP.

practical work are abundant, and the instruments required in the
early stages are very simple.

Full instructions will be found for carrying out the experiments
given in the following pages, and if the student will only per-
form them, and carefully make notes of the results obtained, he
will, after working through the book, have a good working
acquaintance with elementary botany.

SUMMARY.

Botany concerns itself with the study of plants. It is a concrete
science.

Boundary lines can be easily drawn between the higher plants and
the higher animals, but the line of demarcation is difficult to define
when the lower forms of life are under consideration.

Plants and animals are built up of protoplasm. The tree of life is a
forked one.

DIFFERENCE BETWEEN LIVING AND NON-LIVING BODIES.

Living.

1. Their shape is definite.

2. Can reproduce their kind.

3. Can take in food and grow
internally.

Non-Living.

1. Either of no definite shape
or crystalline.

2. Cannot reproduce their kind.

3. Cannot take in food and can
only grow from the outside.

The one object of the plant is to reproduce its kind.

Morphology

the science of shape
and structure. It is
divided into —

Anatomy or struc-
ture made out with-
out the use of the com-
pound microscope.

Histology or struc-
ture made out by the
use of a compound
microscope.

SCOPE OF THE SUBJECT.

Physiology

j the science of func-
I tion, or what a plant
can do. It is divided
into —

Physiology of nutri-
tion.

Physiology of move-
ment.

Physiology of re-
production.

Classification.

the science of rela-
tionship.

Embracing plant
description, and plac-
ing the plant in its
true position in the
natural system.

INTRODUCTION

QUESTIONS ON CHAPTER I

(1) Define the term botany. What are the objects of botany?

(2) What is meant by a concrete science? Why is botany placed
among the concrete sciences ?

(3) Can a clear boundary line be drawn between the higher animals
and the higher plants ? If so, why ?

(4) Into what divisions can botany be divided ? Why is botany
divided into the divisions you mention ?

(5) Give a short account of the natural system of classification.

(6) What is meant by the life-history of a plant ?

(7) Why is practical work of such great importance in natural history ?

CHAPTER II

MORPHOLOGY.— STUDY OF THE BODY OF A PLANT

Parts of a Plant. — If any ordinary plant, such as a wall-
flower or mustard plant, be examined, we find that it consists of
certain well defined parts.

These parts are known as root and shoot ; the shoot can
again be divided into stem and leaf.

The root and stem are continuous, and together form the
axis of the plant. The root is called the descending axis, and
the stem the ascending axis. By the repetition of these parts
a plant is built up. From a morphological point of view, these
parts of a plant are termed its members, and they can be
classified under four main heads, as follows : —

1. Root-structures. — These are as a general rule found at
the base of the plant. They serve to fix it to the soil, and to take
in water and minerals. The root of the mustard plant may be
mentioned as a typical instance.

2. Stem-structures. — These may be aerial, as in the stem
of the oak, that is, those which grow upwards into the air ; or,
they may be found beneath the soil, as in Solomon's Seal, when
they are called subterranean stems. In some cases, like the
strawberry, they creep along the surface of the ground, when they
are known as creeping stems. From the stem both leaves and
buds are developed as lateral outgrowths.

3. Leaf-structures. — Leaves are, as a general rule, thin,
and green or brightly coloured. They are produced by the
stem.

CH. II

MORPHOLOGY

4. Hair-structures.— These may grow from all .parts of the
plant and may be short, or long and silky. All hair structures
agree in being developed from the epidermis or skin-like
coverings of the plant. Some hair-structures serve to keep off
unwelcome guests, like ants ; others again, like those of the
horse chestnut, secrete or form a kind of glue to protect the
young buds from cold ; while
some, like the dandelion, take
part in scattering the seeds.

Organs.— From a physio-
logical standpoint the parts
of a plant are spoken of as
its organs. An organ is a
structure which is able to
perform some special work,
e.g., the root is an organ be-
cause it fixes the plant to the
soil.

EXPT. i.— Obtain a nearly
full-grown Wallflower plant, and
examine it. "Observe —

(i) The shoot is erect and
branched, and the older part is
hard and woody. The upper
part of the shoot is green, and
the lower part of it is covered
with a pale- brown bark.

(ii) That the shoot can be
divided into stem and leaf — the
leaves being outgrowths of the
stem.

(iii) That the stem branches,
and the branches rise from the
space between the stem and
leaves. The space between the
leaf and stem is called the axil
of the leaf (Fig. 3).

(iv) That the leaves are green, thin, veined, and lance-shaped.

(v) The shoot is hairy, the hairs lying very close to the surface. Pass
the leaf through the ringers and note what the hairs feel like.

(vi) That the main root is nearly colourless and tapers from the point
where it joins the stem to its apex. Springing from the main root will
be seen a very large number of secondary roots, or root branches, which
help to fix the plant to the soil.

FIG. 2.— Wallflower Plant.

BOTANY FOR BEGINNERS

CHAP.

The stock, or any ordinary plant will do for this experiment.

The body of the wallflower is built up of the same members as
are found in an oak tree (Fig. 4), a potato, or many other plants.

The Parts Present
in a Seed.— Most flower-
ing plants are produced
from seeds, and at this
point it will be well to
consider the structure of
seeds. The same parts
can be found in a seed as
have been recognised in
the wallflower, along with
other parts which belong
to the parent plant.
The Structure of a

FIG. 3. — Stem and leaf; showing axil. Bean.

EXPT. 2. — Soak a , few

Scarlet Runner beans in water for twenty-four hours, and examine one
of them. Note —

(i) The bean is kidney-shaped, and along one side is a dark scar — the
hilum — -where the seed was attached to its stalk.

VV '

FIG. 4.— Oak Tree.

(ii) The small hole near the hilum — the micTQpyle. It can be seen
best by wiping the seed and gently squeezing it, when water will ooze out.

MORPHOLOGY

(iii) If the point of a penknife or a pin be inserted opposite to the
hilum, the seed-coats can be removed. The seed-coat, or Spermoderm,
consists of two layers ; the outer is known as the testa, anuthlT'Tfiner
is called the tegmen.

(iv) The seed-coats surround a whitish mass, which may fall in pieces ;
this is the young plant or embryo.

(v) If the embryo is examined there will be found along the side near
to the micropyle a small body, called the radicle, the apex of which
points towards the micropyle.

(vi) Now separate the white mass, along the middle line, into its two
divisions — the se§d-leaves or cotyledons.

(vii) Between the cotyledons will be found the plumule or young
stem, which is continuous with the radicle, and if you use a lens

FIG. 5.— Bean Seed. A = A side view of seed. B = Showing radicle. C = Bean,
with seed coats stripped off. D = Seed coats. E = The two cotyledons.
F = Plumule/

you will be able to see a number of minute leaves growing from the
plumule.

(viii) It care be taken in examining the embryo, it will be noticed
that the radicle, plumule, and cotyledons are all joined together to form
the body of the embryo.

We can represent the relations of the parts of the bean seed
as follows : —

Bean.

Embryo.

Cove

rings.

Cotyledons, Plumule, Testa.

1
Tegmen.

Radicle,

or young root, or seed leaves, or young stem.

Structure of a Grain of Wheat.—

EXPT. 3. — Take a few grains of Indian Corn, and soak them in
water for a few hours, and examine in the following way : — Cut the
grain lengthwise with a sharp knife, and look at half of it with a hand
lens. Observe —

(i) The covering, which is made up of several layers, only two of

12 BOTANY FOR BEGINNERS CHAP.

which correspond to the testa and tegmen of the bean. The other
layers belong to the fruit, for the grain of wheat is in reality a fruit
(p. 19).

(ii) The micropyle is hidden by the coverings of the fruit and cannot
be seen, but at one -end of the grain a firmer portion will be found,
which is the embryo, and above the embryo a softer portion, the
endosperm, can be distinguished. This is reserve food material for the
use of the young plant.

(iii) On the cut surface of the embryo, in contact with the endosperm,
a single cotyledon will be found ; and on the outside of this an upper
portion, the plumule, and a lower portion, the radicle, can be made
out.

The following table will show the relation of the different
parts found in the grain of Indian Corn.

Indian Corn.

I I.

Kernel. Covering.

L_ _ I

I I I " I

Embryo. Endosperm. Spermoderm. Fruit.

I I I

Radicle. Cotyledon. Plumule.

Dicotyledons and Monocotyledons.— In both the Bean
and Indian Corn seeds, the embryo consists of radicle, plumule
and cotyledons, but the number of cotyledons differs.

The Indian Corn has only one cotyledon, but the Bean
possesses two. Those plants which possess two cotyledons are
referred to as Dicotyledons, and those with only one as
Monocotyledons. The Bean belongs to the former, and the
Indian corn to the latter.

Germination of Seeds. — The early stages of the develop-
ment of the embryo are spoken of as germination. If the seed
is examined during germination, we can clearly see how the
various parts which are found in the embryo act during that
process.

EXPT. 4. — Obtain a few Mustard seeds, and place them on a piece
of flannel stretched on a saucer. Keep the flannel damp and warm.
Examine the seeds from day to day, and notice : —

(i) That they begin to sprout. This is the result of the moisture and
heat. At one place a small swelling appears, which is due to the radicle
pushing its way through the micropyle.

MORPHOLOGY

(ii) In a few days the radVJe will have grSwn into the primary or
main root, and from it a laree numtar of secondary roots develop.

FIG. 6.— Pot of Mustard seedlings,
showing cotyledonary leaves.

FIG. 7. — Pot of Mustard seedlings,
showing secondary leaves.

Drainayc - -

FIG. 8. — How to pot a plant.

(iii) The plumule grows upwards towards the light and the cotyledons
are green.

EXPT. 5. — Take a few of the young Mustard plants used in the last
experiment and a plant pot with soil in, and with a penholder make a

BOTANY FOR BEGINNERS

CHAP.

few holes in the soil. Plant the mustard seedlings, firmly pressing the
soil to the roots. Water the soil ,and place the pot on a window sill.
Examine every day, and notice that ther'apex of the stem gives off
new leaves, and that these new leaves are very different from the seed
leaves.

EXPT. 6. — Take some of the seeds of the Indian Corn used in
Experiment 3, and, as before, plant them in a box or plant pot, and
notice that—

(i) The plumule is the first part to appear above the soil, and its tip
is surrounded by the cotyledon.

(ii) Carefully remove a plant from the soil ; the primary root or radicle
is very short, and from it are produced a very large number of
adventitious roots.

FIG. 9. — A Maize seedling, showing
roots and leaves.

FIG. 10. — Adventitious roots of a
Grass.

Adventitious roots are those roots which are not produced in
regular order. Roots are also given off from the plumule just
above the cotyledon. The difference between primary, secondary,
and adventitious roots is well seen in the mustard and in the
Indian corn. Primary roots are always formed by the elonga-
tion of the radicle ; the secondary roots grow from the radicle,
in regular order ; but adventitious roots are produced from the
stem, or some part of the plant other than the primary root.

MORPHOLOGY 15

SUMMARY.

Farts of a Plant. — The body of a plant is built up of root and shoot.
The shoot is divided into stem and leaf. The axis of the plant is built
up of the root and stem. The root is the descending axis and the stem
the ascending axis.

From a morphological point of view, we speak of the various parts
of a plant as members ; these members are classed as root-structures,
stem-structures, leaf-structures, and hair-structures.

The members are termed organs if we treat them from a physiological
standpoint. The wallflower plant is built up of the same parts as the
oak tree.

Farts in a Seed. — The following tables show the parts present in the
seeds of the Bean and Indian Corn.

Bean. Indian Corn.

Coverings of Fruit. Absent. Coverings of Fruit. Present.

Seed-Coats. Testa and tegmen. Seed-Coats. Testa and tegmen.

Embryo is built up of radicle, Embryo is built up of radicle,

plumule, and two cotyledons. j plumule, and one cotyledon.

Endosperm. Absent. Endosperm. Present.

Marking in seed coat the hilum. i Marking in seed coat, not seen.

Opening. Micropyle. Opening. Micropyle, not seen.

This is a Dicotyledonous plant, j This is a Monocotyledonous

because it possesses two cotyle- plant because it only possesses

dons. one cotyledon.

By the germination of the seed we mean the changes that a seed goes
through during its early development.

A Primary Boot is a root which is produced by the elongation of the
radicle. A secondary root is a root which is produced from the primary
root. Adventitious roots are roots which are produced from any part of
the plant and without any regular order.

QUESTIONS ON CHAPTER II.

(1) Define the term member. Name the members which can be
found in any plant you may select.

(2) What is the use of a root ? What kinds of roots are there ?
(1881.)

(3) Suppose a piece of the axis of some flowering plant were shown
to you, what appearances would enable you to decide whether it was
part of the root or of a stem ? (1882. )

(4} Describe the structure of a grain of wheat, and the mode of its
germination. (1888.)

(5) Describe and compare the seeds of the bean and of the wheat.
(1887.)

(6) From what part of a stem does a branch grow ? Illustrate your
answer by a sketch.

CHAPTER III

ANATOMY — STUDY OF THE SHOOT

Shoot. — Stems and leaves are so intimately connected that
it is impossible to treat of one without reference to the other.
The term shoot is therefore used to include both the stem and
its leaves. At the apex of the shoot there is, as a general rule,
the growing point, from which the leaves and branches are pro-
duced. The leaves increase in size faster than the stem, which
causes them to overlap the apex, forming a bud. The structure
of the tip of the shoot can be made out by the aid of a hand lens.
The growing point will be found at the apex of the shoot and
it is surrounded by a number of minute leaves.

EXPT. 7. — Take a twig of the Horse Chestnut, and make a longi-
tudinal section so as to pass through the apex.

Examine the section by the aid of a hand lens. A series of leaves,
the largest on the outside and the smallest near the centre of the bud,
will be found, and protected from injury by these overlapping leaves,
the growing point will be fairly easily made out.

Buds. — A bud is an undeveloped shoot, and from it leaves
and branches may be produced. Buds receive different names
according to the parts of the plant which may be produced from
them. If a bud develops into a branch it is known as a stem-
bud, if foliage leaves are formed from the bud it is called a
leaf-bud ; a flower-bud is one which produces a flower.

Buds are often named after their position on the shoot. If
the bud is found at the end of the shoot it is called a terminal
bud ; when it grows in the axil of a leaf, an axillary bud ; if
the bud springs from any other part of the shoot it is known as

CH. Ill

ANATOMY— STUDY OF THE SHOOT

an adventitious bud, but these are very rare though the ten-
drils of the vine are produced from such buds.

Some buds may be latent or dormant, i.e., remain undeveloped
for a long time. These may become active when the ordinary
buds have been destroyed by frost or accident. Trees in spring
may have their leaves destroyed by frost, but after a few weeks
a new set of leaves are developed, which are formed from latent

buds. Latent buds may thus
save the life of the tree. Even
when in the dormant state these
buds increase in size and give
• T rise to balls such as are often

seen, under the bark, in the
Beech, Chestnut, and Lime.
Latent buds also give rise to the

FIG. ii.— Twig showing; T, Ter-
minal buds ; L, Lateral buds.

Fig. 12. — Stem and leaves, showing buds in
the axils of leaves.

knots which are found in timber. If the main shoot of the Oak
and Beech be cut down, a dense outgrowth of branches, formed
from the base of the shoot, occurs ; this is called tillering. The
new outgrowth is formed from the dormant and adventitious
buds. It is a very common practice for farmers in the spring
to roll the wheat which is sown in winter ; this is to make it

i8 BOTANY FOR BEGINNERS CHAP.

tiller. In other cases they have the young growing points
eaten off by sheep to produce the same result.

Those buds which persist through the winter are protected
with special bud-scales, which may be membranous or scaly in
their texture. The bud-scales of the Oak are dry, those of the
Horse-Chestnut sticky, from the secretion which they produce.

FIG. 13.— Tillering of Stump of Elm.

In some cases bud-scales may be hairy, and in others perfectly
smooth. The bud-scales as a general rule fall off as the bud
opens, thus allowing the leaves to expand.

EXPT. 8.— Obtain a small branch of the Hazel, and note the position
of the buds. That at the apex of the branch is the terminal bud, those
behind are the lateral ones.

EXPT. 9. —Take a twig from any tree in winter, and keep it in water
in a warm room. Note —

(i) It will produce leaves from the leaf-buds ; if flower buds are
present, flowers may be produced.

(ii) This experiment shows that the materials necessary for the de-
velopment of the leaves and flowers are stored up in the tree, and when
the necessary temperature is obtained development takes place.

in ANATOMY— STUDY OF THE SHOOT 19

EXPT. 10. — Cut sections through the apex of the buds of the Horse
Chestnut and Sycamore. Note —

(i) The overlapping scale leaves.

(ii) The young foliage leaves.

(iii) The apical growing point.

(iv) The arrangement of the different parts should be shown in a
sketch.

Kinds of Plants. — Plants may be annual, biennial, or
perennial, i.e., they may last one, two, or more years.

Annual Plants produce seeds during the first year of growth
and then die. Wheat, Barley, Peas, Beans and Mignonette, are
examples.

Biennial Plants are those which during the first year of
growth store up reserve materials, these substances being used
for the production of flowers and seeds in the second season.
Thus, biennial plants must live two years. Turnip, Cabbage,
Foxglove, and Beet, are typical examples.

Perennial Plants live and grow for three or more years.
They may be trees or shrubs, such as the Oak, Beech, and
Hawthorn ; or they may be herbs, like the Daisy, Snowdrop,
Wild Hyacinth, and Primrose. The herbaceous perennials
have underground stems from which the leaves and flowers are
produced ; the aerial parts die down each season.

The Ascending Axis. — The ascending axis is a very
important part of the plant ; though leaves may be absent, and
in a few cases roots may not be developed, the stem is always
present. The stem bears buds, leaves, flowers, and fruits, and
connects the leaves with the roots. If the stem is produced by
the elongation of the plumule, it is called primary or normal.
The place on the stem from which a leaf arises is termed a
node, and the space between two nodes is termed an inter-
node. In some cases the nodes are thickened, as in the
Stitchwort, and in a few cases adventitious roots may spring
from them, as in the Ivy.

Herbaceous Stems.— The ascending axis may be soft
and green, and die down at the end of the season, when it is
called a herbaceous stem. Herbs are plants which fulfil their
life-history in a single season ; they are also called annuals.
Annuals, such as the Stock, Oats, and Indian Corn, also
produce seeds at the end of their period of growth.

C 2

20 BOTANY FOR BEGINNERS CHAP.

Shrubby Stems differ from those named above in being
hard and woody. They are larger than herbaceous stems ; but
smaller than the stems of trees. A shrub is a dwarf tree with
a number of permanent woody stems, which divide from the
bottom. A shrub differs from a tree (a) in the stems being
more slender, and (b) in not growing more than twenty feet high.
The following are typical shrubs : — Box, Heath, Rose, Rhodo-
dendron, Gooseberry and Currant.

HERBACEOUS. SHRUBBYwWOOW STEMS.

FIG. 14. — Diagram illustrating herbaceous, shrubby, and woody stems.
A = Herbaceous. B = Shrubby. C = Woody. S = Section.

Woody Stems are large, and last for a number of years ;
they shoV rings of growth if cut across. Our forest trees such
I^LS the Oak, Beech, Fir, Lime, and Ash have woody stems.
* Aerial Stems grow above the ground, as those of the Oak,
Wallflower, and Foxglove. Several forms of aerial stems are
distinguished : —

The Runner is a stem which creeps along the surface of the
ground, and produces adventitious roots from its underside, and
leaves from its upper surface, e.g., the Strawberry (Fig. 15).

The Off-set is a stem which is produced from the parent stem ;
it creeps along for a short distance and then takes root, e.g., the
House-leek (Fig. 16).

The Stolon is a branch which takes root at its end, thus pro-
ducing a new plant, e.g.) Couch-grass (Fig. 17), Gooseberry, and
Currant.

Ill

ANATOMY— STUDY OF THE SHOOT

The Sucker is an aerial branch given off by an underground
stem ; it runs for a short distance beneath the surface, and then
strikes upwards, forming a new plant, e.g.^ the Rose and Mint.

Subterranean Stems grow beneath the surface of the
ground, and are often termed, in popular language, roots.

FIG. 15. — Runner of Strawberry.

FIG. 16.— The Off-set of the House-leek. FIG. 17.— The stolon of the Couch-grass.

Many perennial plants are able to exist throughout the winter
by means of underground stems.

The Rhizome is a creeping underground stem which produces
both roots and leaves. The roots are produced from the under-
surface of the stem, and the leaves from the upper. Rhizomes

BOTANY FOR BEGINNERS

CHAP.

differ from roots in producing leaves and buds. Solomon's Seal
and the Iris produce rhizomes (Fig. 18).

The Tuber is a swollen underground stem, and in it there is
stored up large quantities of reserve materials for the production

* I c d

FIG. 18. — Rhizome of Solomon's Seal. a = bud of next year's aerial growth
b = scar of this year's growth ; c, d, e, scars of previous year's aerial growth

and iu = roots.

FIG. IQ. — Part of Potato plant, with the old dark tuber in the centre.
(One-third natural size.)

of a new plant. The Potato tubers are produced from the ends
of stolons, and thus are formed a little distance from the parent

Ill

ANATOMY-STUDY OF THE SHOOT

plant. The so-called eyes that are found on the outside of a

potato are in reality buds, from which the next year's growth

will take place. The parent plant

dies after the production of tubers,

but not before large stores of reserve

materials have been accumulated in

the tubers for future use. If the

aerial branches of the Potato plant be

covered up with soil, their growth

will be checked and they will produce

tubers. The Jerusalem Artichoke and

the Earth-nut also produce tubers.

The Bulb is a modified stem often
met with in monocotyledonous plants.
It consists of a short thickened stem
with a large number of crowded, over-
lapping leaves. These leaves contain
a large quantity of reserve material
for the growth of the next season's
plant. In the Onion the leaves
sheathe one another, but in the Tiger
Lily they only overlap. The bulb is
closely allied to the tuber. The
Onion, Wild Hyacinth, and Daffodil
are examples of plants that produce

bulbs.

The Corm is a

very solid fleshy

stem with fewer

leaves than che bulb. In the Crocus it is a

solid, rounded, main axis, full of reserve

materials. The Snowdrop and Gladiolus

spring from corms.

EXPT. ii. — Obtain from a gardener a piece

of the runner of a Strawberry plant. Note —
r IG. 21. — Corm of /-\ tr it. re

Crocus. w H°w the runner gives off roots.

(ii) How the leaves are produced. The leaves
are developed from the upper surface of the

stem and from the nodes 5- the roots spring from the lower surface
of the stem.

FIG. 20. — Longitudinal section
of bulb of Tulip, zk, modi-
fled stem ; zs, scale leaves ;
57, terminal bud ; k, young
bud ; w, roots.

24 BOTANY FOR BEGINNERS CHAP.

EXPT. 12.— Take a few plants of the Couch grass — which can be
found in most meadows and in cornfields, and examine them. Select
one which shows the stolon best. Note —

That the branch is given off above the level of the ground, and then
bends downwards and forms a root at the end.

EXPT. 13. — If a piece of a sucker of a Raspberry plant with its attach-
ment to the underground stem be obtained, the way in which it is pro-
duced can be noted. It will be seen that the underground stem
produces a branch, which runs for a short distance beneath the ground
and then breaks through the soil and comes to the surface.

EXPT. 14. — Dig up a rhizome, either of Solomon's Seal or a Bracken
Fern. To do this it is necessary to have a good trowel with which to
remove the surface soil. Follow the stem so as to uncover it without
breaking it, and examine. Note —

(i) The old scars produced by the leaves of previous years. These
are caused by the dying down of the leaves.

(ii) The new leaves, which will break through the ground next
season.

(iii) The growing point, which is protected by scale leaves.

EXPT. 15. — Take a Potato tuber and examine it. The eyes, which
are buds, will be seen as small dark spots. If a young tuber be examined,
the minute scale leaves round the growing point will be seen. Cut a
tuber in two and notice how thick and fleshy it is.

EXPT. 1 6. — Obtain a-bulb of the Daffodil and a Crocus corm. Examine
and compare them. Note —

(i) The bulb which is made up of scale leaves, many of which are
thick and fleshy.

(ii) In the corm the stem is far larger than in the bulb, but the leaves
are not so numerous.

Parasitic Steins. — In a few cases stems are so modified
that they can fix themselves to another plant, and extract from
it those materials which are necessary for their existence.
Plants of this description are called parasites. The Dodder
is a good example of such a plant ; it can live on the
Clover, the Nettle, and the Willow. When the seeds of the
Dodder germinate a long filament is formed, the free end of
which moves round and round in search of a host plant — as
the plant upon which it lives is called — and when a suitable
plant is found it twines closely about it like a climbing plant.
Suckers are produced from those parts of the filament which are
in close contact with the host, and these pierce the host, and
work their way inwards, to obtain food.

Ill

ANATOMY— STUDY OF THE SHOOT

EXPT. 17. — If a specimen of a plant can be obtained, which has been
attacked by the Dodder, it should be examined. Note —
(i) How the Dodder climbs round the host,
(ii) How the suckers are produced.

Climbing Plants.— Plants climb over the shoulders of
their weaker brethren for two reasons ; (a) because their shoots
are far too weak to sup-
port their own weight,
and (b) to expose their
leaves to light. Climbing
plants present four divi-
sions, viz. : (i) Those
which climb by the aid of
rootlets, as the Ivy. (2) By
the use of hooks, as the
Bramble and the Yellow
Bedstraw. (3) By twining
stems, as the Convolvulus
and the Hop. (4) By
sensitive organs which
come in contact with any
structure and clasp it, as
the Clematis and the
Vine.

Rootlet-Climbers.-
The Ivy climbs by means
of adventitious roots
which are produced from
the stem. When these
come in contact with a
wall or the bark of a tree
they give out a fluid, which
by drying up causes the
stem to adhere to the

support. The rootlets are produced on the shady side of the
stem, and in older stems may not all be fixed to the support, but
may be "dried up, forming shaggy beards (Fig. 22).

Hook-Climbers. — The Bramble is able to support itself by
weaving its way through the trees which grow in its neighbour-
hood. It is able to do this because it produces hooks, by the aid

FIG. 22. — Ivy climbing up a wall.
R = Aerial roots.

BOTANY FOR BEGINNERS

CHAP.

of which it fixes itself to walls, trees and shrubs. Cleavers,

which is a struggling, rough and matted plant found in hedges,

is another good example of a plant which climbs by means of

hooks (Fig. 23).
Stem -Climbers. — When the stem of the hop plant comes

out of the ground its first

two or three internodes grow

up erect. The young inter-
nodes which are produced

from the top of the first-
formed portion commence to

bend slowly and gracefully

to one side and travel

steadily round to every point

of the compass, describing

a complete circle in the

direction the minute hand

of a watch moves over its

face. Should the twining

stem of the Hop come in

contact with a support, the

part which it strikes is seized FlG- 23--The hooks of the Bramble.

by the hooks which are well

developed on the stem. The stem still grows at the apex and

goes on twining, thus climbing more and more about the

support. The Bindweed or Convolvulus also climbs by means

of twining stems, but these
climb in the opposite direc-
tion to the Hop, i.e., to-
wards the left. The stems
of the Hop and Honey-
suckle turn round from the
west through the south
towards the east ; this is
called twining to the right.
The Scarlet Runner and

FIG. 24.— Diagram illustrating how plants
twine. The left-hand figure shows how
the Honeysuckle twines to the right ; the

ight-hand figure how the Convolvulus

wines to the left.

twines to the

the Bind-weed turn round

.from the west through the north towards the east ; this is
termed twining to the left (Fig. 24).
Plants which Climb with Sensitive Organs.— This

Ill

ANATOMY-STUDY OF THE SHOOT

division can be subdivided into two classes, w>., leaf-climbers
and tendril-climbers.

A good example of a leaf climber is the familiar Clematis.
The upper, younger internode of the Clematis goes wandering
round and round in slow circles after the manner of the twining

FIG. 25. — Climbing stem of Honey-
suckle. (One-fourth nat. size.)

FIG. 26. — Climbing stem of Con-
volvulus. (One-fourth nat. size.)

plants. This brings the leaves in contact with the stems, twigs,
or the trellis-work erected by the hand of man. Such objects
as these are seized slowly but surely by the leaf-stalks of those
leaves which come in contact with them. The leaf stalks are
sensitive and turn round the object touched.

A tendril is another structure which is sensitive to touch and

BOTANY FOR BEGINNERS

CHAP.

Is used for climbing. These organs, with their ready response to
any contact and their power of turning round and clinging to
objects, are the most highly developed in the class of climbing
plants. Tendrils are formed from various parts of plants ; thus,
in the Passion flower it is a whole branch transformed ; the
tendril of the Vine is a flower-stalk ; that of the Sweet Pea, the
whole blade of a leaf ; that of the Cucumber and its allies arise

by the alteration of the leaf-like
bodies found at the base of the
leaf-stalk and known as stipules.
The tendrils, like the twining stem,
move round and round in search of
a support.

Some tendrils, when their move-
ments are arrested by a support,
form adhesive masses at their free
ends, as in the Virginian creeper,
which is so often seen covering the
sides of houses. Soon after the
tendrils of the Virginian creeper
have laid themselves down, as it
were, upon a wall, their tips swell,
become red and form little swollen
cushions. On the parts in con-
tact with the wall, small pro-
jections are produced which in-
sinuate themselves into every little
crevice and seem to give out a
cement which binds them to the
support (Fig. 27).

FIG. 27. — Virginian Creeper.
R, R, stem tendrils. (Three-
fourths nat. size.)

EXPT. 1 8. — Obtain a piece of Ivy
from an old wall ; examine it. Note
the following points —

(i) That a portion of the wall has come away with the roots,
(ii) That the roots grow on a portion of the stem which is turned
away, from the light.

(iii) That the root dries up, and forms a beard on the stem.

EXPT. 19.— Examine branches of the Rose or Bramble. Notice—
(i) The prickles ; pull one or two off and see how much of the
branch comes away with them.

(ii) Prickles may be used for protection as well as for climbing.

Ill

ANATOMY— STUDY OF THE SHOOT

EXPT. 20. — Obtain a portion of the Hop-plant or Honeysuckle with
its support. Note —

(i) How and in what direction the stem has moved. Compare with
a piece of the Scarlet Runner and Bindweed.

(ii) Note the difference in the direction of twining.

EXPT. 21. — Obtain from a hedgerow or garden a piece of Clematis
showing the sensitive leaf-stalks. Examine how the stalks clasp the
support.

EXPT. 22. — Obtain a tendril-bearing plant, such as the Vine, Vetch,
Sweet Pea, Cucumber, or Bryony. Examine to see what parts of the
plant have been modified in the production of the tendril. Compare
with a portion of the Virginian Creeper.

The Shape of the Stem. — Stems may be round or cylin-
drical^ as in the Lily ; triangular, as in the flower stem of the
Daffodil ; square, like the Deadnettle ; or ribbed, like the Wall-
flower (Figs. 28 — 32).

FIG. 28.
Round stem,
with section.

FIG. 29.
Square stem,
with section.

FIG. 30.

Ribbed

stem, with

section.

FIG. 31.
Triangular
stem, with

section.

FIG. 32.

Coarsely-
ribbed stem,
with section.

Some stems are solid at the nodes, but hollow at the internodes,
e.g.* FooFs-Parsley. Others are solid throughout as in the
Wallflower.

Surface of the Stem.— Stems differ not only in their shapes
but also as regards the nature of their surfaces. Many stems
are completely covered with hairs, prickles, or thorns. If the
surface is smooth, it is termed glabrous ; if hairs are present,
hairy.

BOTANY FOR BEGINNERS

CHAP.

The Wallflower is covered with spindle-shaped hairs, and
upon the Stock branched hairs are found.

In the Stinging Nettle large hairs for protection are found.
When the tip of such a hair enters the finger it breaks off and a
fluid is injected into the wound causing a well-known
smarting sensation.

The surface of a stem may be covered with prickly structures,
which may be produced by the modification of hairs, or other
structures. The hooks on the stems of the Hop, Cleavers, arid

Borage are true
hair-structures, be-
cause they are de-
veloped from the
surface layer of the
plant. The struc-
tures found on the
stem of the Sloe,
and which are
fo rm ed from
branches which
have undergone
change so as to
protect the plant
from its enemies,
are called thorns.
The prickles of
the Hawthorn are
modified leaves ;
they are, as a rule,
termed spines. The
prickles of the

Bramble and Rose are formed not only by the development
of the surface covering of the plant, but also by a deeper layer
which takes part in their formation. The name emergences
may be given to them.

EXPT. 23. — Cut across the stems of the following so as to show
their shape :— Wallflower (old stem), and flower stems of the Daffodil,
Lily, Deadnettle, and Mignonette. Compare their shapes and notice if
the stems are solid or hollow.

EXPT. 24.— Examine as many stems as possible to see if they are

FIG. 33. — Spines on the Hawthorn.

in ANATOMY— STUDY OF THE SHOOT 31

smooth or hairy. Similarly describe the surface of every stem met
with. If this is done for a few weeks, the reader will have a very
valuable series of notes.

EXPT. 25.— Collect a few branches of the following plants : Haw-
thorn, Rose, Sloe, Bramble, Hop, Cleavers, Borage, and prickly
Comfrey. Examine and make notes of the size of the prickles, thorns,
spines, and emergences found on them. Sections should be made
through the stem so as to show the connection of the covering with
the underlying parts.

Leaves. — Leaves are developed as lateral outgrowths from
the growing point of the stem. They are often said to be
flattened out stems. They may be deciduous, that is, they may
fall off from the stem each year ; or persistent, remaining on the
tree for a number of years. The Oak produces the former kind
of leaves and the Holly the latter.

Leaves are developed in regular order, the older ones being
found on the base of the young twig and the younger ones near
the apex. There are four kinds of leaves which grow on the
stem. They are :—

Foliage-leaves, or the ordinary green leaves of the plant.

Scale-leaves, or those found covering the bud.

Bracteate-leaves are found close to the flower, which they as
a general rule protect.

Floral-leaves ; some of these are coloured, and the flower is
built up by them.

All these kinds of leaves are not found on every plant. Most
plants possess foliage leaves, but the Dodder has only scale
leaves. In the Lily of the Valley, the foliage leaves, bracts and
floral leaves are all developed. In the Wallflower only the first
and last are found.

EXPT. 26. — Collect branches of the Oak and Fir in winter.
Notice that the twigs of the Oak are without leaves, but the Fir is
well covered with them.

SUMMARY.

Shoot. — Built up of stem and leaf. The growing point is at the apex,
and is surrounded by leaves.

A bud is an undeveloped shoot. There are three kinds of buds, viz. ,
stem-buds, leaf -buds, and flower-buds. The bud at the apex of a stem
is called the terminal bud, and those behind lateral^ and if the latter

32 BOTANY FOR BEGINNERS CHAP.

are produced in the axils of the leaves they are axillary buds. An
adventitious bud is one which is produced out of the regular order. A
latent or dormant bud is one which remains undeveloped.

Tillering is a term which is used to describe what takes place when
a plant produces a large number of branches from the base of the stem.

Plants can be divided into (i) A nnual plants ; these only live a
single season. (2) Biennial plants ; these during their first year of
growth produce foliage leaves and store up food, and during the
second season produce flowers and seeds. They only live two years.
(3) Perennial plants live three years or more.

The ascending axis produces leaves, and connects the leaves with
the roots. The places on the stem from which leaves spring are
termed nodes, and the space between two nodes is called an internode.

Stems. — There are three kinds of stems.

Herbaceous.

Soft and green, and
die down each year.

Shrubby.

Hard and woody,
not above twenty feet
high.

Woody.

These are hard and
strong, and grow "Vvwo
twenty feet high.

above

Aerial Stems grow above the ground. They can be divided into :
The Runner, which creeps along the ground, like the Strawberry. The
Offset creeps along the ground for a distance from the parent, then roots.
The Stolon is a branch which takes root at its end. The Sticker is
given off from an underground stem. The Erect Stem grows upright
like the Oak.

Subterranean Stems grow beneath the ground and can be divided
into : The Rhizome, which creeps along beneath the ground and pro-
duces both roots and leaves. The Tuber is a swollen underground stem
which grows from the end of a stolon. The Bulb is a fleshy under-
ground bud, and is modified for the storing up of food for future use.
The Corm is a solid, fleshy, underground stem.

Parasitic Stems are produced by parasites. A parasite is a plant
which is too lazy to earn its own living, so lives on a host .plant. The
Clover Dodder is a good example of such a plant.

Climbing Plants. — There are four classes of these plants. They are as
follows : Rootlet Climbers, like the Ivy. Hook Climbers, like the
Bramble. Stem Climbers, like the Hop and Convolvulus. Plants
which climb with sensitive organs ; they can be divided into (a) leaf
and (b] tendril climbers.

Stems. — They may be round, square, ribbed, and triangular. They
may be smooth or hairy. The surface may be covered with spines or
emergences.

Leaves are produced as outgrowths of the growing point of the stem.
There are four kinds of leaves found growing on the stem : Folio ge
Leaves are the ordinary green leaves of the plant. Scale Leaves are
found on the roots and young buds. Bracteate Leaves are found at the
base of the flowers. Floral Leaves are modified leaves which go to
build up the flower.

in ANATOMY- STUDY OF THE SHOOT 33

QUESTIONS ON CHAPTER III.

1 i ) Of what use to the plant is the stem ? How can you distinguish
a stem from a root ?

(2) What are the essential differences between a node and an
internode ? Illustrate your answer by examples. (1884.)

(3) What is a rhizome, and how does it differ from a root? Explain
the mode of annual growth in length of the rhizome of Solomon's Seal.
(1885.)

(4) State what is meant by annual, biennial and perennial plants,
giving examples. (1886.)

(5) What do you know about —

(a) The runner, (b) The rhizome,

(c\ The tuber, (d) The offset,

(e) The bulb, (/) The corm ?

(6) What kinds of stems are there ? Give examples.

(7) Where is the growing point of a shoot found, and how is it
protected from injury ?

(8) If all the leaves on a Currant bush be plucked in spring, what
will happen ?

(9) How are the knots found in thnber produced ?

(10) Define the term " tillering." When and how does tillering take
place ?

( 1 1 ) What is a parasite ? Give an account of the mode of life of the
Dodder.

(12) Give examples of plants which climb by means of tendrils, and
explain how the tendrils act. (1887.)

(13) Give a classification of climbing plants. Why do plants climb ?
How do they climb ?

(14) What is the structural difference between a prickle (as in the
Rose) and a spine (as in the Blackthorn) ? (1881.)

CHAPTER IV

THE STUDY OF THE SHOOT (Continued)

Parts present in a Perfect Foliage Leaf.— In a perfect
leaf the following parts are present.

The blade or the fully expanded portion of the leaf.
I\\R petiole or the stalk of the leaf.

The Sheath which forms the base of the leaf. It is wider than
the petiole, and may sheathe the stem.

In most cases the blade is present ; when other parts of the
leaf are absent, the leaf is said to be sessile, as in the Wall-
flower. If the sheath is not developed, but
the blade and petiole are present, the leaf
is called petiolate, as in the Cherry. If all
the parts are present, as in the Pilewort and
Arum, the leaf is perfect. Outgrowths may
be produced from the base of the leaf, as in
the Rose and the Pea ; these are termed
Stipules. If stipules are present the leaf is
said to be stipulate, and if they are absent
exstipulate.

The Venation of Leaves.— The veins
of a leaf form the framework by which the
softer parts are supported ; they also bring
the sap from the stem and distribute it to
the cells of the leaf. Leaves may either be
parallel or reticulate — veined. The former
arrangement is found in monocotyledonous plants and the
latter in dicotyledonous. In a parallel- veined leaf, the veins
run parallel to one another from the base of the blade to

-B

FIG. 34.— Perfect leaf
of Arum. B =
blade ; P = peti-
ole ; sh =sheath.

CH. IV

THE STUDY OF THE SHOOT

the apex, and they are connected by smaller cross veins, as in

the leaf of the Lily of the Valley. The reticulate-veined leaf

differs from the parallel-veined leaf

in possessing one or more midribs,

from which veins are produced

eventually uniting with one another

to give the leaf the appearance of

net-work. The Oak bears such a

reticulate-veined leaf (Fig. 36).

If the leaf only possesses one
mid-rib, the leaf is said to be uni-
costate. When the leaf is divided
into a number of divisions, and each
lobe possesses a mid-rib, it is said
to be multicostate. The leaves of
the Oak, Beech, Poppy, and Dan-
delion, are unicostate, while the
leaves of the Monkshood, Castor-
oil plant, and Fig, are multicostate.

The veins of a leaf give it

strength ; it depends upon the mode of life of the plant what
kind of leaves will be produced. Plants which grow in a very

FIG. 35. — Venation of a leaf.

FIG. 36.— Unicostate leaf of Oak.

FIG. 37. — Multicostate and palmate leaf
of the Horse-Chestnut.

exposed position generally have narrower leaves than those
which grow in sheltered places. Water plants with submerged

D 2

BOTANY FOR BEGINNERS

CHAP.

leaves have the veins finely divided so as to give mechanical
support, as well as to expose as great a surface to the water as
possible. In the case of marsh plants like the water Crowfoot,
which has two kinds of leaves, it is only the submerged ones
which are divided.

Ex FT. 27. — Collect a number of leaves and arrange them into —

(i) Two series according to their venation.

(ii) The two divisions, unicostate and multicostate.

Arrangement of Leaves on the Stem.— Leaves grow
from the nodes of the stem, and the arrangement of these

FIG. 38. — Alternate leaves of
Rhododendron.

FIG. 39. — Opposite leaves of
Privet.

depends upon the length of the internodes and the size of the
leaves. The leaves on a given plant are always inserted at
points which bear a certain relation to one another, which may
be expressed in a numerical manner. The arrangement of
leaves on a stem is often spoken of as phyllotaxis. If one
leaf only is produced at a given node, and from the node higher
up the stem but on the opposite side another springs the
phyllotaxis is said to be alternate, as in the Wallflower.

THE STUDY OF THE SHOOT

When two leaves spring from the node and face each other, the
arrangement is called opposite ; if the leaves higher up are
placed at right angles to the first pair, the arrangement is called
decussate — the Deadnettle is a good example of this. If more
than two leaves are produced at a node, they are termed
whorled leaves. The
Bed-straw and Cleavers
illustrate this arrange-
ment.

The most common ar-
rangements of leaves are
the alternate, opposite,
and whorled. The so-
called alternate arrange-

Start of Spiral
Twig ofOaJc .

FIG. 40. -Whorled leaves of
Cleavers.

FIG. 41. — Diagram illustrating £ phyllo-
taxis of Oak.

ment can be further investigated by drawing a spiral round the
stem from one leaf until the leaf vertically above is reached. In
the case of the Wallflower or Oak the spiral goes round the stem
twice before the leaf vertically above is reached, and five leaves,
not counting the leaf at which the spiral commenced, are touched
by the -spiral. This is known as a £ arrangement. The same
phyllotaxis is found in the Pear, Poplar, and Walnut. In the
Plantainthe leaves form a $ phyllotaxis.

BOTANY FOR BEGINNERS

CHAP.

FIG. 42.— Diagram
illustrating f
phyllotaxis.

FIG. 43. — Diagram
illustrating ^
phyllotaxis.

simple when the blade consists
Elm, Holly, and Dead-
nettle. The blade may
be divided, but, unless it
is cut down to the mid-
rib, it is still a simple
leaf. Compound leaves
are cut into a number of
distinct pieces, as in the
Pea and the Ash. Each
separate part of such a
leaf is called a leaflet.

Simple Leaves. —
Leaves vary much in
shape or general outline. FIG.

EXPT. 28. — Collect and ex-
amine branches of the Oak,
Wallflower, Deadnettle, Bed-
straw, and Elm. Determine
their phyllotaxis, and mark on
the stem the leaf-cycle or the
cycle made in passing from one
leaf to the leaf vertically above.
This can be done with a piece
of coloured chalk, and if the
leaves are also numbered the
arrangement will be seen at a
glance.

Different Kinds of
Foliage Leaves. — When
the leaves spring from an
underground stem, as in the
Daisy and Dandelion, they
are called radical leaves.
If^ they grow on an aerial
stem, as the leaves of the
Oak and Wallflower, they
are spoken of as cauline
leaves.

Foliage leaves may be
either simple or com-
pound. Leaves are called
of a single piece, as in the

44. — Radical leaves of the Primrose.

THE STUDY OF THE SHOOT

Simple leaves receive the following names, according to the
shape of the blade :—

Lanceolate ', when the leaf is from two to four times as long as
it is broad and tapers at both ends, e.g., Wallflower (Fig. 45).

Ovate, when the broadest part is nearer the base than the
apex, e.g. Guelder-Rose (Fig. 46).

Cordate, when the base is shaped like a heart, e.g. Lime
(Fig. 47).

Sagittate, when the base possesses pointed ends extending like
an arrow backwards, e.g. Convolvulus (Fig. 48).

Obovate, when the broadest end is nearer the apex than
the base, e.g. as in some of the Rock- Roses, and leaflet of
Wood-Sorrel (Fig. 49).

Fici. 45.— Lanceolate
leaf of Wallflower.

Fig. 46.— Ovate leaf of
Lilac. '

FIG. 47. — Cordate leaf
of Deadnettle.

Oblanceolate, when the lanceolate leaf has a wider part
which is nearer the apex than the base, e.g. Dog Violet and
Spurge Laurel (Fig. 50).

Spatulate, when the leaf is like a spoon, with a rounded
portion near the apex, e.g. Daisy.

Reniform, when the leaf is kidney-shaped, e.g. Ground Ivy
(Fig. 52).

Linear, when the leaf is very long and narrow, e.g. most
Grasses (Fig. 53).

Elliptical, when the leaf is oval, e.g Apple (Fig. 54).

Acicular, when shaped like a needle, e.g. Fir.

BOTANY FOR BEGINNERS

CHAP.

Many of the above terms are used to describe the shapes of
the leaflets of compound leaves.

FIG. 48. — Sagittate FIG. 49. — Obovate FIG. 50. — Diagram FIG. 51. — Spatulate

leaf of Arum. leaflet of Wood- of Oblancaolate leaf of Daisy.

Sorrel. leaf.

Compound Leaves.— If the blade of the leaf is divided
down to the mid-rib it is said to be compound. The separate
parts of the blades are called leaflets ; these are given off from

FIG. 52 — Reniform leaf
of Ground Ivy.

FIG. 53. — Diagram of
linear leaf.

FIG. 54.— Elliptical
leaf of Apple.

the mid-rib. The leaflets separate from the mid-rib or petiole
in the same way that the entire leaf separates from the stem, /.<?.,
without tearing. They may be pinnately or palmately divided.
The following are examples of the latter kind.

THE STUDY OF THE SHOOT

Ternate or trifoliate, the leaf is built up of three leaflets, as in
the Clover and Wood-Sorrel (Fig. 55).

Bitemate, when the leaf is ternate, but each division is
divided again ; in fact, three leaflets divided into three leaflets, as
in the Baneberryor Herb Christopher.
Palmate, when the leaflets radiate
from the leaf-stalk like fingers from
the palm of the hand, e.g., Horse-
Chestnut (Fig. 37),

When the leaflets are arranged
along each side of the midrib, they are
said to be like a feather or pinnate.

FIG. 55.— Ternate leaf of
Wood-Sorrel.

FIG. 56. — Ternate leaf of Strawberry.

FIG. 57.— Biternate leaf of
Baneberry.

There are two kinds of pinnately divided leaves — those with
an equal number of leaflets along each side of the mid-rib, and
those with an odd leaflet. The former are called paripinnate,
and the latter iinparipinnate.

Paripinnate, when there are an equal number of leaflets on
each side of the mid-rib, as in the Bitter Vetch.

BOTANY FOR BEGINNERS

CHAP.

Imparipinnate, when there is an odd leaflet, as in the Rose
and Robinia (Fig. 58).

Bipinnate, when the leaflet is again divided, as in the common
Meadow Rue and Acacia (Fig. 59).

Tripinnate, when the division is carried a little farther and
each part is in three, as in the Lesser Meadow Rue.

The Margin of Leaves.— The margin of leaves vary in
different plants. The following terms are used to describe
them : —

Entire, if the margin is undivided, as in the Wallflower
(Fig. 60).

FIG. 58. — Imparipinnate
leaf of Robinia.

FIG. 59.— Bipinnate leaf of Acacia.

Serrate, if the margin is divided up into teeth-like divisions,
like a saw, and they point towards the apex, the above term is
used, ^>.,Deadnettle.

Biserrate, if the teeth are again divided, as in the Elm.

Crenate, if the teeth are rounded, as in the Ground Ivy.

Dentate, if the teeth point outwards, as in the Guelder Rose.

THE STUDY OF THE SHOOT

Ciliated, if the margin is fringed with fine hairs like the
Beech.

Spiny , if the teeth are long and very sharp, as in the Holly.

Apex of the Leaf— The apex of the leaf may be sharply
pointed, when it is called acute ; if blunt, Obtuse ; and if the end
is long and pointed, acuminate (Fig. 61).

Further Kinds of Simple Leaves.— When the leaf is

FIG. 60. — Diagram of margin of leaves, i, biserrate ; 2, serrate ; 3, crenate
4, spiny ; 5, entire ; 6, dentate ; 7, sinuate.

split up into a number of divisions, and these do not cut down
to the mid-rib, the following terms are used : —

Palmatisect, if the ends extend nearly to the base, e.g.,
Monkshood.

Palmatifid, if the cuts extend about halfway from the margin
to the base of the leaf, as in the Castor Oil plant.

Palmate, if in the palmatifid leaf the number of divisions is
five, as in the Maple.

BOTANY FOR BEGINNERS

CHAP.

Pinnatisect, if the divisions extend nearly to the mid-rib, as in
the Poppy.

Pinnatifid, if the cuts extend about half way from the margin

FIG. 61. — Diagram of apex of leaves. A, acuminate ; B, obtuse ; C, acute ;
D, mucronate ; E, retuse ; F, emarginate.

to the midrib, as in the Welsh Poppy, and in some of the leaves
of the Mignonette.

Lobed Leaves. These, according to the number of lobes, may
be trifid) trilobed, five-lobed, &c.

EXPT. 29. — Make a collection of leaves. Note and compare their
shapes with the figures in the book.

The leaves can be dried by pressing them widi heavy weights between
the leaves of a blotting book or even between sheets of note paper. If
the sheets of paper be changed every day until the leaves are perfectly

THE STUDY OF THE SHOOT 45

dry, the leaves can be mounted on sheets of card board, or on special
papers such as the following : —

.6 in

4 in

Shape.
Margin.
Apex.
Venation.
Name of plant.

EXPT. 30. — Try and cut out in paper the different forms of any leaves
which may be obtained. This can be done by laying the leaf on a sheet
of white paper and tracing on the paper with a fine pointed pencil the
outline of the leaf. Cut along the lines so made with a sharp pair of
scissors. The name of the leaf and its shape can be marked on the
model. The pupil will soon discover how difficult it is to describe the
leaf with accuracy, and will also apprehend the greater truth that there
are probably not two leaves alike.

EXPT. 31. — Examine every leaf, spine, and tendril you can obtain.

Stipules. — These, as we have already seen, are outgrowths
at the base of the leaf. The texture and colour of stipules vary ;
thus, if their function is to protect the young leaves in the bud,
they may be brown or yellow in colour ; if they are used for
assimilation, that is, to provide nourishment for the plant, they
are green in colour, and large and leaf-like in form.

There may be two stipules, one on each side of the leaf, as in
the Pea and Pansy. In some of the Bed-straws the stipules are
large and are often mistaken for leaves ; in fact, they appear to form
whorls with the leaves. The stipules are membranous in the
Rose leaf, where they are represented by a series of teeth along
each side of the base, and are called adnate stipules. Where

BOTANY FOR BEGINNERS

CHAP.

the stipules unite in the leaf-axil they are called axillary^ as in
the Pea (Fig. 62).

Scale Leaves. — Scale leaves possess a far simpler structure
than foliage leaves. They have no leaf-stalk, and are directly
attached to the stem. Their principal function is to protect
the young buds, and they are the only leaves found on under-
ground stems. A few parasitic plants, such as the Broom Rape

FIG. 62.— Leaf of Pea. Fi, flower-
stalk ; SP, stipules ; T, tendrils.

FIG. 63.— Leaf of Rose. L, leaflets ;
P, petiole ; sf, stipules.

which grows on the roots of plants, do not possess any other
kinds of leaves.

Bracteate Leaves. — Bracteate leaves resemble scale leaves
both in structure and function. They grow at the base of the
stem upon which the flowers are produced. When present the
plant is said to be bracteate, if they are absent, ebracteate.
Bracts may be scaly, leafy, membranous, woody, or coloured.
When the bracts are arranged in a circle, as in the Dandelion,
they form an involucre. If the bracts form a solid cup, as in the

THE STUDY OF THE SHOOT

acorn, they form a cupule. When a single bract is large and
protects a series of flowers it is called a Spathe, e.g., the Arum.

EXPT. 32. — Examine the leaf of a Pea and find the stipules. Note —
The stipules are large and leaf-like. Observe how the end of the mid-
rib of the compound leaf is converted into a tendril. Compare with the
stipules of a Rose leaf.

EXPT. 33. — Note the size, shape, and characters of as many scale
leaves as possible during spring, when the buds are opening.

FIG. 64. — Transverse section of leaf-bud
of Water Lily, (x 6.)

Fig. 65.— Bracteate leaf of
Narcissus. B, bract.

FIG. 66. — Transverse section through
leaf-bud of Lilac. (X 5.)

Floral Leaves. — Floral leaves are modified leaves which
go to build up the flowers of a flowering plant.

Vernation. — The way in which the young leaves are
folded in the bud is called vernation or prcefoliation. This
differs in different plants, and will be considered under two
heads, viz., (a] the folding of the individual leaf in the bud ; and
(V) the folding of the several leaves in the bud.

BOTANY FOR BEGINNERS

CHAP.

The arrangement of the individual leaf in the bud is shown
below in a tabular form : —

i. — If the leaf is not folded at all, the vernation \^ plane.

2. — If the leaf is folded along the mid-rib, it is conduplicate,
e.g.) Bean.

3. — If the leaf is folded into a number of longitudinal or
oblique pleats, it is plicate, e.g., Beech.

4. — If the leaf is folded in all directions, it is crumpled, e.g.,
Poppy.

5. — If the leaf is folded inwards towards the mid-rib, it is
involute, e.g., Violet.

FIG. 67.— Transverse sec-
tion of leaf-bud of Ash.
(X7-)

FIG. 68.— Transverse
section through leaf-
bud of Beech. (X6.)

6. — If the leaf is folded backwards towards the mid-rib, it is
revolute, e.g.", Dock.

7. — If the leaf is folded up from one side to the other, it is
convolute, e.g., Banana.

The arrangement of the several leaves in the bud is shown
below : —

i. — If the leaves in a bud just touch by their margins, the
vernation is valvate.

2. — If the leaves in a bud overlap each other, it is imbricated.

3. — If the leaves in a bud overlap each other in regular order,
it is twisted or contorted.

4. — If the outer conduplicated leaves in a bud enclose those
within in regular order, it is equitant.

THE STUDY OF THE SHOOT

5. — If half of one conduplicated leaf enfolds another, it is
seini-equitant.

6. — If one convolute leaf is rolled around another, it is
supervolute.

EXPT. 34. — Cut a transverse section of any leaf- buds met with.
Note—

(i) The arrangement of the individual leaves in the bud.

(ii) The arrangement of the several
leaves in the bud.

(iii) The arrangement of the parts in
the buds. Show it by sketches.

SUMMARY

A Perfect leaf consists of a sheath,
petiole, and blade. If the blade is the only
part present, the leaf is said to be sessile,
and petiolate when the blade and petiole
are developed.

Stipules are outgrowths at . the base
of the leaf. Leaves can be exstipulate
or stipulate.

Venation of leaves — two kinds — parallel and reticulate.

Phyllotaxis is the arrangement of leaves on a stem. The common
arrangements are alternate, opposite, and whorled.

Foliage Leaves may be simple or compound. In the former the blade
is not divided down to the mid-rib, but in the latter kind the blade is
cut up in separate or distinct parts.

FIG. 69. — Transverse section
of leaf-bud of Sycamore.
(X4.)

Simple leaves may be
Lanceolate. Oblanceolate.
Ovate.
Cordate.
Sagittate.
Spatulate.

Obovate.
Reniform.
Linear.
Elliptical.
Acicular.

Compound leaves may be
Ternate. Paripinnate.

Biternate. Irnparipinnate.
Palmate. Bipinnate.

Tripinnate.

The Margin of Leaves may be— (i) Entire, (2) Serrate, (3) Biserrate,
(4) Crenate, (5) Dentate, (6) Ciliated, (7) Spiny.

The Apex may be— (i) Acute, (2) Obtuse, (3) Acuminate.

The Margin may be divided as— (i) Palmatisect, (2) Pinnatifid,
(3) Pinnatisect, (4) Palmatifid, (5) Palmate, (6) Lobed.

Stipules may be leaf-like, or membranous.

Scale Leaves.— These are found to be modified leaves ; they protect
the buds from injury.

Bracteate Leaves. —These are found at the base of the flowers, and
may form an involucre, cupule, or spathe.

50 BOTANY FOR BEGINNERS CH. iv

Floral Leaves. — From these various parts of the flowers are formed.
They can be divided into four kinds.
Vernation or Praefoliation is the folding of the leaves in the bud.

QUESTIONS ON CHAPTER IV.

(1) What is a leaf? Excluding the leaves forming the flower, we
have three kinds occupying different positions on the stem in the higher
plants. Briefly describe these.

(2) (a) What parts are present in a perfect foliage leaf? (b] What
kinds of venation are found in leaves ? »

(3) Give instances of leaves which are only imperfectly developed.
What useful purposes may they serve in such cases? (1882.)

(4) What is the general plan of arrangement of leaves on a stem ?
Why is it the most advantageous to the plant ? (1881.)

(5) Give a botanical description of the part, in each of the following
plants, which is commonly used as food : the potato, the onion, the
turnip, and the carrot. (1887.)

(6) Describe, with examples, the principal forms of compound
leaves. What is the difference between a simple and a compound
leaf? (1890.)

(7) Explain, with examples, the following terms : — Bract, stipule,
pinna, petiole, peduncle. (1896.)

. (8) What are stipules ? Describe the stipules of the Rose and the
Sweet Pea.

(9) How do the leaves of the Oak differ from the leaves of the Clover ?

(10) Describe the general structure of the leaf-bud, explaining the
meaning of the term " vernation." What is the usual position in which
buds are developed on the stem? (1891.)

CHAPTER V

ANATOMY— STUDY OF ROOTS

Descending axis.— The descending axis, or root, is the
part of the plant which grows downwards, fixes it into the soil,
and takes from the ground water in which minerals are dissolved.
The root can be distinguished from the stem in the following
way : —

ROOT.

1. The root produces neither
leaves nor buds.

2. The root as a rule grows
downwards.

3. The growing point of a
root is protected by a sheath
which is called the Boot cap.

4. The root produces small
hairs, which absorb from the
soil the water and minerals
required by the plant for its
growth.

5. Roots grow away from
the light.

EXPT. 35. — Dig up a Deadnettle and examine it.

(i) The roots bear neither leaves nor buds.

(ii) The stem produces both.

(iii) The hairs on the stem, which are close set and are used to protect
the plants from cold currents of air and from insect pests.

(iv) The very minute and soft hairs on the roots. These can be best
seen if the root be held up between the eye and the light and looked at
through a hand-lens.

£ 2

STEM.

1. The stem produces both
leaves and buds.

2. The stem as a rule grows
upwards.

3. The growing point of the
stem is protected by scale
leaves.

4. The stem produces hairs ;
but these are as a rule used for
protection, and not for obtain-
ing food.

5. Stems grow towards the
light.

Note—

BOTANY FOR BEGINNERS

CHAP.

EXPT. 36. — Take a few Beans and soak them in water for twenty-
four hours. With a sharp knife cut longitudinal slices from the radicle
and place them on a glass slip, such as is used for microscope work.
Hold the glass slip between the eye and a strong light and place the
hand-lens up to the eye. Move the sections first
towards the lens and then away from it, until they
appear clear. Near the apex of the radicle a dark
inner portion and an outer lighter part can be
made out. The dark portion is the growing point,
and the lighter part the root-cap.

The Primary Roots.— The root pro-
duced by the elongation of the radicle is
termed a primary root. When the primary
root persists and continues to grow it is
called a tap-root. The Oak, Bean, and
Wallflower produce tap roots. Branches
are produced from the primary root in regu-
lar order, the oldest being found towards its
base, i.e., near the apex or growing point.

The Secondary Roots.— The lateral
branches of the primary root are termed
secondary roots. They differ from the
branches of the stem in not being produced
in the axil of leaves, nor from buds ; but they are formed in
regular order. Each plant produces a definite number of rows of
rootlets, which are arranged longitudinally, the roots in each row
being accurately one above the other. The secondary roots grow
horizontally or somewhat obliquely, not straight down like
primary roots, and in this way the roots between them parcel out
the soil. In the Wallflower there are four rows of roots, which
strike out north, south, east and west, and it is clear that
between them there is always unoccupied ground. This
unoccupied ground is worked by roots produced from secondary
roots and known as tertiary. They have no definite direction
of growth, but spread outwards, upwards, and in all directions,
thus reaching every part of the vacant soil.

EXPT. 37. — Obtain a Wallflower plant with perfect roots. Wash the
roots in water so as to remove the soil.
Examine the roots and observe —
(i) The primary root.

(ii) The secondary roots forming four rows,
(iii) The tertiary roots growing from the secondary roots.

FIG. 70.— A Mustard
seedling, showing
root - hairs and
cotyledons.

ANATOMY— STUDY OF ROOTS

EXPT. 38. — Compare the roots of the Deadnettle, or any other plant
which can be obtained, with the Wallflower, and note the number
of rows of secondary roots.

Adventitious Boots. — The roots which are produced
without any definite order from stems, leaves and roots are
termed adventitious. In most monocotyledonous plants the
primary root is either very short or ceases to grow soon after it
leaves the seed. Its place is taken by an immense number of
adventitious roots which spring from the stem. When gardeners
place cuttings in the soil, they are said to " strike " when they

FIG. 71. — The fibrous roots of a Grass.

FIG. 72. — Branches of a Gooseberry
bush producing adventitious roots.

take root. This is brought about by adventitious roots being
produced from the nodes of the stem which is pushed into the
soil.

Clinging Roots. — When adventitious roots are used for
climbing as in the Ivy, they are called climbing or clinging
roots. Roots of this kind are very highly developed in many
tropical plants like the Orchids.

54 BOTANY FOR BEGINNERS CHAP.

Such roots simply cling to the bark of trees, they take nothing
from the plant on which it grows. Some water plants produce
a large number of roots which float in the water and help to
support or moor the plant. The Duckweed, which grows in
many of our ponds, is a good example.

EXPT. 39. — Dig up a Grass plant from a field, and examine the roots.
Note—

(i) The tap-root is either absent or very short.

(ii) A large number of roots, which seem to come from either the top
of the root or from the stem, and grow without any regular order, can
easily be made out. They are called adventitious roots. They are
also fibrous roots.

Aerial Roots. — Adventitious roots which hang down in the
air are called aerial roots. Epiphytes are plants which possess
such aerial roots. The aerial roots of some plants can obtain
water from the atmosphere and dissolve any mineral matter
which may be blown against them. Many Tree Ferns, Aroids,
and Orchids are epiphytes. The Vine may, in some cases,
produce aerial roots which hang from the stem in rich profusion
and most likely help to obtain water for the plant. Some aerial
roots are green, and perform the same work as leaves. They
may reach the ground and take root as in the Banyan tree.
The Ivy clings to the bark of trees and to old walls by means of
aerial roots which are produced from the shady side of the
stem.

Water Roots. — The roots of plants which float or grow in
water are known as water roots. They may be developed either
from stems with floating foliage leaves, or from stems with sub-
merged leaves. Floating roots never penetrate even the mud at
the bottom of a pond : but the roots of marsh plants go right
down into the mud. The ordinary roots of Willows, Alders,
and Elms, growing along the sides of streams, often grow from
the bank into the water in which they float. Water roots do not
produce root hairs.

EXPT. 40. — Obtain a Hyacinth bulb, and place it in a vase of water.
Make up the loss of water which will take place by a solution1 con-
taining—

Potassium nitrate . I gram. Calcium phosphate \ gram.
Sodium chloride . . \ ,, Water . . . .1 litre
Calcium sulphate . . | ,, Iron chloride . . a few drops
Magnesium sulphate. \ ,,

1 Any chemist will make up this solution.

ANATOMY— STUDY OF ROOTS 55

Such a solution contains everything necessary for the growth of a
plant. Note how the bulb produces water roots, which obtain from
the solution the substances required by the plant for its growth. Observe
the growth of leaves and flowers. This experiment shows that roots,
which under natural conditions live in soil, can change their mode of
life and become water roots.

EXPT. 41. — Cut a slip from any plant, (the garden Geranium will do),
so as to leave at least three nodes with leaves and one without. Place
the slip in a bottle with some of the solution used in the last experiment.

Observe that roots develop in the water from the nodes. Keep the
bottle warm ; it will soon be filled .with roots. These roots are
adventitious and aquatic.

Parasitic Roots.— The roots of those plants which pene-
trate a host plant, and extract nourishment from it, are called
parasitic. The Mistletoe, which grows on Apple, Fir, and

FIG. 73. — St, stem of Apple. S, shoot of Mistletoe ; R, roots of Mistletoe.
(One-twelfth nat. size.)

Poplar trees is a parasite. Mistletoe is very plentiful in our
homes about Christmas time, and most persons know its berries.
Thrushes feed on these berries, and the seeds enclosed in the
fruit are protected from the digestive juices by a hard covering.
They consequently pass out of the digestive tube without
undergoing any change ; the droppings of the Thrush are

BOTANY FOR BEGINNERS

CHAP.

generally voided from the upper branches of trees and carry the
seeds with them. The droppings and the seeds which are
enclosed in them cling to the branches. The seeds germinate
and the radicle which is produced is pressed closed to the bark
and cemented there (Fig. 73).

The Eye-bright, so common in fields, produces suckers on its
root which attach themselves to the roots of grasses and extract
nourishment from them. The Yellow-rattle, Lousewort, COW-

FIG. 74. — Conical root of Carrot.

FIG. 75. — Napiform root of Turnip.

wheat, Toothwort, and Broom-Rape, are all parasites growing on
the roots of plants.

EXPT. 42. — Pull up a few plants of Eye-bright and examine their
roots. Find the suckers, which appear as little white knobs on the
roots ; they are always found on the secondary roots.

Modified Boots. — Roots may be modified for the storing up
of reserve materials, often becoming large and fleshy, as in the

ANATOMY— STUDY OF ROOTS

case of the Turnip. Roots of this description belong to
biennial plants. The principal shapes of modified roots are as
follows : —

i. — Conical^ when broad near the stem and tapering towards
the tip, as in the Carrot (Fig. 74).

2. — Napiform, when shaped like a Turnip. The Swede
usually has, at the crown of the root, a neck from which the leaves
spring. This is absent in the Turnip (Fig. 75).

3. — Fusiform, when the root tapers both near the stem and
towards the apex, e.g., Radish (Fig. 76).

FIG. 76. — Fusiform
root of Radish.

FIG. 77.— Nodular or tubercular root of
Pilewort.

4. — Tubercular, when the rootlets are swollen and round, as in
the Pilewort (Fig. 77).

EXPT. 43.— Obtain the roots of the Turnip, Carrot, and Radish.
Make sketches illustrating their shape, and mark on them the reduction
in size which you make. This can be done by measuring the size of
the root, and then the drawing . If these be compared, the reduction
can be found. The pupil should do this in all sketches made.

EXPT. 44. — Dig up, either in March or April, the roots of the Pile-

58 BOTANY FOR BEGINNERS CHAP.

wort. This plant can be distinguished from the common Buttercup,
because —

(i) Its leaves are cordate and perfect ; in the Buttercup the leaves are
very much divided, and the segments are lobed.

(ii) The petals vary in number from eight to ten ; in the Buttercup
there are only five. Examine the roots and note the swollen fibres ;
these are used for storing up reserve materials. These are tubercular
roots.

Uses of Boots. — Roots perform various functions which
can be arranged in a tabular form.

1. Roots fix the plant in the soil. The roots can anchor a
tree like the Oak so that the strongest wind cannot blow it over.
In many cases the roots of grass-like plants are used by
engineers, to bind together the soil along an embankment,
and so keep it from falling, as on the West Coast of Lancashire
and in North Italy.

2. Roots obtain nourishment from the soil. The roots parcel
out the soil so that nutritive materials can be extracted from
every part by the root-hairs. All the water given out by the
leaves of a plant is obtained by the root-hairs from the soil. The
roots make good the loss of water which takes place through
the leaves.

3. Roots may be used as a store-house for material to enable
the plant to produce flowers and seeds during the next season.
In this case the roots are swollen and large.

4. Roots may be used for climbing, floating, or to enter a host
plant. The shape, size, and method of growth of roots will
depend upon their function.

EXPT. 45. — Obtain any plant growing in a plant pot. Cover over
the soil, either with card-board or tin-foil, to prevent evaporation
from the pot. Place the plant beneath a glass globe, and expose to
light in a window sill. Note that the inside of the glass is soon covered
with moisture. This is given out by the leaves, and the loss can only be
made good by the water taken in by the roots.

Movements of Roots.— The younger portions of the roots
are all in a constant state of motion. When the radicle leaves
the seed it commences to move, and so long as life lasts the tip
of the root will go on moving round and round in search of
certain substances or conditions. The force exerted by a young
radicle when growing is very great ; in twenty-four hours it
causes a downward pressure equal to lifting a weight of a

v ANATOMY— STUDY OF ROOTS 59

quarter of a pound. Roots not only move in the direction of least
resistance, but also towards damp and away from dry soil.

The use of these movements to the plant cannot be over-
estimated. If the root made its way through the soil in a
perfectly straight line, not half the favourable spots for food
would be touched ; the spiral or circular movements of the root
ensure its contact with the best sources of food in the soil. The
tip of the root is also very tender and liable to be injured, and
the movement from side to side enables it to find the path along
which there is least danger to the growing point.

EXPT. 46. — Take a few Beans or Peas and germinate them on damp
sawdust. When the radicle appears through the micropyle, turn the
seeds over so that the radicle points upwards. Under another radicle
place a piece of glass. Notice how the radicles act.

EXPT. 47. — Using the Beans or Peas germinated above,

(i) Cut off the root-tip of a radicle, so as to separate it just above the
growing point.

(ii) Place a piece of post card on one side of the tip of a radicle, and
on the other side a piece of tissue paper. This can be done by using a
solution of shellac.

(iii) Cut slices from a few radicles, so as to remove a longitudinal
layer from one side. Great care must be taken not to fix the card too
far away from the tip or the radicle will turn towards the card, not
away from it. Make notes of the results.

EXPT. 48. — Replace one of the sides of a box with a piece of glass.
Fill up the box with alternating layers of sand, sawdust, clay, and peat.
Sow mustard seeds or the seeds of any quick growing plants. Cover up
the front of the box with a piece of cardboard. Keep the box warm
and damp. When the seed leaves are well up in the air, place the box
on a window sill. Remove the cardboard from day to day, to see how
the roots are placed against the glass.

EXPT. 49. — Take the bottom out of a box, and nail on in place of
the bottom a piece of wire netting with holes of about a quarter of an
inch in diameter. Fill the box up with soil, placing the largest particles
at the bottom. Grow plants as in Expt. 48. Hang the box up in a
window and keep the soil moist. Note —

(i) The roots will pass out through the wire netting.

(ii) Many, if not all, will bend up and pass again into the box. This
shows that the radicle or roots like darkness better than light. In fact,
nearly all roots grow away from the light.

SUMMARY.

Roots can be divided into —

Primary roots. — A primary root is produced when the radicle goes
on growing. Thus, all primary roots are produced by the elongation of

60 BOTANY FOR BEGINNERS CHAP, v

radicles. Those roots which are formed from the primary roots are
called secondary roots. When roots grow out of the secondary roots
they are known as tertiary roots.

Other kinds of Roots. — Adventitious roots are produced from stems,
leaves, and roots without any regular order. Clinging roots are adven-
titious roots used to fix a plant to a support. Aerial roots hang down
in the air and take water from it, or enable a plant to climb. Water
roots are produced by water-plants, and do not produce root-hairs.
Parasitic roots penetrate into a host-plant and extract nourishment from
it. Modified roots have undergone a change, so as to serve as a store-
house of reserve material.

Shapes of Roots. — May be conical, napiform, fusiform, tubercular,
fibrous.

Uses of Roots. — (a] They anchor the plant to the soil, (b) They
obtain nourishment from the soil, (c) Food may be stored up in them.
(d) They may be used for climbing, &c.

Movements of Roots. — Roots are always moving from place to place,
so as to find food and the line of least resistance.

QUESTIONS ON CHAPTER V.

(1) Describe and explain, with reference to examples, the peculiarities
of the roots of biennial plants. (1890. )

(2) What is a growing point? How does the growing point of a root
differ from that of the stem ? ( 1 889. )

(3) Briefly describe, giving examples, the principal kinds of roots ;
and explain what are the functions which the various kinds of roots are
specially adapted to perform.

(4) How do roots parcel out the soil ? Give examples.

(5) Give sketches showing (a) conical, (b} napiform, (c) fusiform
roots.

(6) What is an adventitious root ? Mention plants which produce
such roots, and give an account of their function.

(7) What is a parasite ? How do the seeds of the Mistletoe find their
way to the host plant ? How does the seed act when it germinates ?

(8) What is a root parasite ? Give examples.

(9) Of what use is a root ? In what circumstances may a plant
exist without one ?

(10) Explain why the root of a turnip first grows faster than the stem,
and then stops while the stem grows.

(n) Give an account of experiments which you have performed to
show how roots move.

(12) In preparing sketches you have to show the scale. What is
meant by the scale, and how can it be determined ?

CHAPTER VI

SECTION?, HOW TO PREPARE AND EXAMINE THEM

Sections. — To fully investigate the internal structure of a
plant or its members, it is necessary to cut sections of the plant
in various directions. A piece cut out of a stem is called a
section. If the stem is cut across at right
angles to its long axis it is called a trans-
verse section. When the stem is cut along
its long axis, the section made is termed
longitudinal. There are two kinds of
longitudinal sections, radial and tan-
gential. A radial longitudinal section
is one which passes through the organic
centre of the stem. A tangential section
can be made lengthways through the
stem, but does not pass through the cen-
tre. This is illustrated by Figs. 78, 79, 80
and 8 1. When a piece is cut out of a
stem in the plane A, Fig. 78, the section
is transverse. Such a section is shown in
Fig. 79. If the cut is made through B,
Fig. 78, it passes through the organic

centre, and is a radial longitudinal section, as shown in Fig. 80.
The tangential section can be made through the plane C, Fig. 78.
This is shown in Fig. 81.

To make good sections either a very sharp knife or a razor
will be necessary. The shape of the blade will depend upon the
size of the proposed section ; if the area of the section is small,
a hollow-ground razor or knife will give the best results, but for

FIG. 78. — Diagram illus-
trating how to cut sec-
tions. A cut along the
line A gives a transverse
section : along plane B,
a radial section : and
along C, a tangential
section.

BOTANY FOR BEGINNERS

CHAP.

large flat sections a cutting instrument with a flat side must be
used. The section when made may be so thin that light can

FIG. 75. — A transverse
section, cut through
A, Fig. 78.

FIG. 80. — A radial sec-
tion, cut through B,
Fig. 78.

FIG.

nge

section, cut through
C, Fig. 78.

pass through it, when it is said to be transparent. If the section
is thick and no light can pass through it, it is called opaque.

EXPT. 50. — Take a long kidney potato and cut sections from it; they
can be made in three directions, as fol-
lows—

(i) At right angles to its long axis ; this
will be a transverse section.

(ii) Parallel to its long axis, and passing
through the centre ; this will be a radial
longitudinal section.

(iii) Parallel to its long axis, but not
passing through the centre ; this will be a
tangential section.

Mounting Specimens. — After
the sections have been cut they must
be mounted on ordinary microscopic
slips. These are pieces of glass three
inches long by one wide. All fresh
specimens can be mounted in water
for examination by the microscope, but
for examination by a hand lens the dry
. object can often be used. Great care

FIG. 82.— Transverse section J

through a square stem. must be taken to have both the micro-
scopic slip, and objects used in pre-
paring the specimens, perfectly clean, for the slightest
amount of dirt will spoil the section. In mounting the object
in fluid only a small drop of it should be used, just sufficient

HOW TO PREPARE AND EXAMINE SECTIONS 63

to cover the object. For examination under the microscope,
the section must be covered with a cover-glass ; these can be
obtained of different sizes, the one in general use being ^ of an
inch in diameter.

If the plant from which the sections have to be prepared has
been kept in spirits, they must be mounted either in alcohol or
glycerine. The section must never be allowed to dry ; if it
does, air fills up the cells, and the air bubbles, as they are
called, make the specimen appear very dark.

(1) Do not begin to cut sections until you are quite certain what
kind you require. If the sections are to be viewed by the compound
microscope, keep the razor or knife wet by dipping it before each cut
into a glass of water for fresh specimens, and in spirits for materials
which have been preserved in alcohol.

(2) Keep the microscope perfectly clean, and be careful that no
mounting fluid finds its way on to the stage, lens, or any parts of the
instrument.

(3) In mounting the specimen, only just sufficient of the mounting
medium must be used to cover the object. When the cover-glass is put
on, it must on no account be allowed to drop ; one edge must first
touch the mounting fluid and be slowly lowered into position, so as to
spread out the medium and drive out the air. This can be done by
using a needle or pin to support the cover-glass, and with the thumb
and finger of the left hand guide it into position as the needle or pin is
slowly withdrawn.

(4) Always keep the section wet so as to avoid air-bubbles. If air-
bubbles are found in a specimen, they may be removed by gently
warming the slide by placing it over ajar containing hot -water.

(5) If the specimen is intended for future use be careful to label it,
and write on this label the name of plant, portion of plant, direction of
section, mounting fluid, and date.

EXPT. 51. — Take a glass slip, and with a dipping rod place a single
drop of water in the centre. Now place a cover-glass over the drop of
water. This can be done by using a needle or pin to support the cover-
glass, and with the thumb and finger of the left hand guide the cover-
glass into position, at the same time slowly withdrawing the needle or
pin. After a few attempts the pupil will be able to spread out the drop
so as to fill the entire space beneath the cover-glass.

The Structure and use of a Hand-Lens.— A lens is a
transparent substance, usually formed of glass, and is shaped so
as to change the direction of the rays of light which pass through
it. A lens appears to magnify or diminish the size of objects
seen through it. A hand-lens is a piece of glass, suitably
mounted, which possesses the property of magnifying objects.

BOTANY FOR BEGINNERS

CHAP,

One of the best and cheapest for botanical work is shown in
Fig. 83. It is called a triplet, because there are three lenses
mounted so that each one can be used by itself, or in combina-
tion with the others. To use such a lens to view a transparent
object it is necessary to place the lens close to the eye and to move
the specimen about until it appears bright and clear. The
object is said to be in focus when it is best seen. If the
specimen to be examined is opaque, the best way to observe it is
to move both the lens and object until a good view is obtained.
Transparent objects can be seen best with all the three lenses as

Fig. 83. — Diagram illus-
trating hand - lens,
i = low power. 2 =
medium power. 3 =
high power.

FIG. 84.

Diagram

showing
position of
lens when
the highest

power is
used.

Diagram show-
ing position of

lens when

medium power

is used.

FIG. 86.— Diagram illus
trating how to focus a
hand-lens. A, the dis-
tance of the object
from the lens when in
focus with the low
power ; B, with me-
dium ; and C, with
high power.

shown in Fig. 84, but if the objects are opaque, with either lenses
i or 2, or i and 2 combined, as in Fig. 85. In Fig. 86, the
edges of the lenses are shown, and A, B, and C, indicates the
relative distances at which a specimen may be viewed by i, i
and 2 and i, 2, 3, respectively.

EXPT. 52. — Place a little cotton wool between two microscope
slips, and with the hand-lens find out the position in which it has to
be held so as to focus it with (i) the lower power, (ii) the medium
power, (iii) the highest power.

vi HOW TO PREPARE AND EXAMINE SECTIONS 65

Cells. — If a thin transverse section of the stem of the sun-
flower be made, and examined with a hand-lens, a number of
openings will be seen ; these represent the elementary parts
of the plant, and are called cells. The portion of the cell which
surrounds the soft material is called the cell- wall, and in our
section is the most prominent part of the cell. The soft
material receives the name of protoplasm, and is the most
important part of the cell. All plants are built up of cells, and
these are arranged to form definite structures, which receive the
name of tissues.

EXPT. 53. — Obtain a ripe Tomato and mount a small portion
of the inner pulp without water, and examine with a lens. Note — the
cells are very large and oval, the cell-walls are very thin, and a thin
protoplasmic lining can be seen.

EXPT. 54. — Sow some seeds of the Sunflower in soil, and when
the stem is about six inches in length, cut transverse sections of
it. These should be placed in a watch-glass with a fifty % solution of
alcohol to clear them. Mount the thinnest section in glycerine and
examine with a lens. The cells are large and filled with protoplasm,
and are arranged in definite groups,

EXPT. 55. — From a small Beetroot cut a thin transverse section,
mount on a glass slip and examine with a hand-lens. Notice the
cells are filled with coloured cell-sap. Place the section in alcohol
for a few minutes and examine again ; the coloured cell-sap will have
oozed out. This is due to the spirits having killed the protoplasm.

EXPT. 56. — Cut a thin section from a Potato, mount and hold it
on the blade of the knife so that a portion is exposed to the light ;
examine with a hand- lens. Note the cells appear as minute bodies,
dark in colour, due to the air they contain.

Tissues. — If a transverse section of the stem of a Sun-
flower be made and examined (see Fig. 87), the cells are seen
to be arranged in a certain definite manner. On the outside
a single layer of cells is arranged to form a covering to the
stem. This covering forms the epidermis. In all cases the
cells which cover the plant, and protect the deeper parts from
injury, form the epidermal tissue. Within the section a
number of groups of cells can be seen forming a nearly complete
ring ; these are separated from the epidermis by a layer of cells.
This ring of cells forms the vascular tissue of the plant. The
separate groups of cells are called vascular bundles. In the
centre, and between the vascular ring and the epidermis, a

BOTANY FOR BEGINNERS

CHAP.

number of cells can be seen. These fill up the interspaces, and
can be called packing cells, or ground tissu^.

All the higher plants are built up of tissues. These tissues
consist of cells which are grouped together to perform special
work. The three kinds of tissues found in the section of the

stem of the Sun-
flower are also
found in leaves,
roots, and
flowers.

EXPT. 57.— If
the ground under
a Holly Tree be
searched during
autumn a number
of leaves in va-
rious stages of de-
cay will be found.
Some will be
found with the
soft material de
cayed away,
leaving a skeleton
leaf. The veins
of the leaf con-
sist of very hard
material, and have
resisted the action
of the atmosphere
to a greater extent
than the softer
material which has

disappeared. The skeleton leaf consists of vascular tissue, as shown
in Fig. 88, where a small quantity of the epidermis and ground tissue
is shown near the apex of the leaf.

EXPT. 58.— Obtain an old Cabbage-stalk and cut a transverse
section. Such a section is shown in Fig. 89, Examine it with the
aid of a hand-lens, and note —

(i) The epidermis, this is shown at A, Fig. 89.

(ii) A ring of tissue is found between the centre of the stem, see B,
Fig. 89, and the epidermis ; this is made up of vascular bundles.

(iii) In the centre a mass of tissue is found with a number of
cavities in ; this is the pith. Between the epidermis and the vascular
cylinder a ring of tissue can be seen, which is called the cortex. These
cells form the ground tissue of the plant.

(iv) On the outside of the stalk is seen a number of marks.

FIG. 87.— Transverse section of stem of Sunflower
A, epidermis ; B, cortex ; C, vascular ring, (x 7.)

HOW TO PREPARE AND EXAMINE SECTIONS 67

These are the places where the leaves were inserted ; they are called
leaf scars (Fig. 89, D).

EXPT. 59. — Cut a transverse section of a twig of the Lime tree.
Note — that the wood is made up of a number of rings. Each
ring is made up of (a) a dark coloured layer and (b) a light coloured
layer. These are shown in Fig. 90. Each ring represents the amount
of growth which has taken place in one year. The age of the tree can
be told by the number of rings of wood present

FIG.

3.— Skeleton leaf of Holly.
(Half nat. size.)

FIG. 89.— A piece of Cabbage stalk.
A= epidermis ; B = cortex ; C = vas-
cular tissue ; D = leaf scar.

EXPT. 60. — Cut in autumn a longitudinal section of the stem of the
Horse-Chestnut so as to pass through the base of a leaf. Examine such
a section with a hand-lens. Note —

(i) The base of the leaf which is connected with the stem (see A,
Fig. 91).

(ii) A layer of cork which consists of cells ; the layer passes right across
(see B, Fig. 91) the base of the leaf. This layer, when the leaf has
performed all its work, separates the leaf from the stem and covers up
the scar which is left.

EXPT. 61. — Cut a transverse section of the stem of the Maize,
and mount it in glycerine. If the stem has been preserved in alcohol
so much the better, because there will be a smaller number of air bubbles
present, and the section will be far clearer. Examine with the low
power of the hand-lens. Note —

(i) The primary cortex. This surrounds the vascular bundles and
helps to support the plant in an erect position.

V 2

BOTANY FOR BEGINNERS

CHAP.

(ii) The ground tissue which separates the vascular bundles, and in
which they are embedded.

(iii) The vascular bundles which are scattered ; they are not arranged
in the form of a ring as in the Sunflower. The bundles are smallest

and most numerous near the primary
cortex, and largest and few in number
near the centre of the stem.

All plants with scattered vascular

FIG. oo. — A piece of the stem 01
the Lime, showing annual
rings.

FIG. oi. — Longitudinal section of stem of
Horse-Chestnut. A, base of leaf;
B, cork layer. ( X 3.)

bundles belong to the Monocotyledons, and those with the bundles
arranged in a ring to the Dicotyledons.

FIG. 92. — Longitudinal section of stem of Sycamore, showing leaf fall and buds in
the axils of leaves, (x 4.)

EXPT. 62. — Select an old root of the Maize from which a number of
rootlets are growing. Cut transverse sections so as to pass through one
of the young rootlets. Select one of the thinnest and mount in water or
glycerine. Examine with a hand-lens. Note —

(i) The young rootlet which is found on one side of the section.
(Fig. 93, R.)

vi HOW TO PREPARE AND EXAMINE SECTIONS 69

(ii) The way the rootlet springs from close up to the vascular bundles,
and breaks through the cortex and epidermis.

EXPT. 63. — Dig up a few rhizomes of the Sweet Flag (Acorus). It
can be found growing in ditches in Lancashire, Yorkshire, Somerset,
Sussex, and in Scotland and Ireland.

Select a young one and cut transverse sections ; choose a thin section

and mount it in glycerine. Examine,
and note —

(i) The scattered vascular bundles
(Fig. 94).

(ii) The vascular cylinder formed
by the numerous vascular bundles.

FIG. 93. — Transverse section of the
root of Maize. R, R, roots. (Xi2.)

FIG. 94. — Transverse section of the
rhizome of the Sweet Flag, (x 2.)

(iii) A few roots which spring from close up to the vascular bundles
may also be seen ; in Fig. 94 they can be seen breaking their way
through the external tissues.

EXPT. 64. — From a stem of the
Vegetable Marrow cut transverse
sections. Select a thin one from
these and mount it in water. Ex-
amine and note —

(i) The pith (which may have
dropped out).

(ii) The vascular bundles in which

ere are a number of large open
essels.

(iii) The epidermis which presents
a sinuous outline.

EXPT. 65. — Make a thin trans-
verse section through the wood of
the Pine which has been kept in FIG.
alcohol for some time to remove the
resin. Mount in glycerine, and
examine. Note —

(i) The cells ; these are small and close together (Fig. 97) in one part
of the section, but large in the remaining portion.

(ii) The small thick walled cells are formed in late summer and autumn,

95-— Tr
>fVezeU

of Vegetable Marrow. The middle
of section has dropped out. (X 5.)

BOTANY FOR BEGINNERS

CHAP.

the larger ones in spring and early summer. The small cells are dark
coloured ; these form the dark portion of the annual ring. The large
cells are light coloured and form the lighter coloured portion of the
annual ring.

EXPT. 66 — Cut a radial longitudinal section through a young stem of
the Pine. Note—

(i) The cells are cut through lengthwise (Fig. 96), and some of them
show a pitted arrangement.

(ii) A few fine lines will seem to cross the section in different parts ;
these are the walls of cells which are cut across transversely.

EXPT. 67.— Prepare a transverse section of a young root of the Pine,
which has been kept in spirits for some time. The root should not

FIG. 96.— Radial section
of wood of Pins.
(X5-)

FIG. 97. — Transverse sec-
tion of wood of Pine.
(X6.)

FIG. 98. — Transverse sec-
tion of young root of
Pine. (X 7.)

be above \ of an inch in diameter. Mount in glycerine. Examine
with a hand-lens. Note —

(i) Around the outer part a series of cells which are arranged in
regular rows ; these are cork cells, and form the protecting tissue of
the root.

(ii) A number of annual rings which have the same appearance as
those seen in the section of the stem of the Lime.

EXPT. 68. — Make a number of transverse sections through the stem
of the Rose on which prickles are found. Select a thin section which
passes through a prickle.

If this is examined by the aid of a hand-lens, the prickle will be
seen to arise not only from the epidermis (Fig. 99), but also from a
portion of the cortex.

EXPT. 69.— Obtain a leaf of the Rhododendron, and bleach it by-
placing it in alcohol for a few hours. Cut a thin transverse section.
This can be done by placing the leaf between slices of Potato, Carrot, or
Elder pith. If a sharp razor be used, and slices be cut across the
embedding substance so as to pass through the leaf, a number of sections
will be obtained. Place these in water or alcohol in a watch glass, and

vi HOW TO PREPARE AND EXAMINE SECTIONS 71

pick out the thinnest. Mount in glycerine. Examine with the high
power of the hand -lens. Note —

(i) The mid-rib, which is the most prominent part of the section. In
the centre of this a vascular bundle will be seen,
(ii) The epidermis which covers the whole
surface of the leaf.

(iii) The ground tissue which comes between
the lower epidermis and the upper.

How to Use a Compound Microscope —

The following is a set of rules to direct the
student how to use the compound micro-
scope : —

(1) Before commencing to use the micro-
scope it must be examined to see if it is per-
fectly clean. If any mounting media or
reagents find their way on to the stage, clean
them off at once with a soft clean cloth.

(2) To examine the lenses, the light must be
directed up through the tube by the mirror.
If the eye-piece be rotated, and specks of
dust move with it, they are on the lenses of the
eye-piece. The lenses must be unscrewed, and
the dust cleaned off with a soft silk rag. If the

dust does not rotate with the eye-piece, it is on the objective, which must
be cleaned in the same way. If either glycerine or Canada balsam is
smeared on the objective, it must be cleaned by a jet of water directed
on to it from a wash-bottle and then be carefully dried. Canada
balsam is removed easily by alcohol or benzol.

(3) To examine a specimen on a slide — screw on the low power
objective, and move the mirror until the whole field is illuminated.

FIG. 99. — Transverse
section of stem and
prickle of Dog Rose.
(X 4.)

FIG. zoo.— Transverse section of leaf of Rhododendron. ( X 8.)

Then rack the tube down until it nearly touches the slide ; if the tube is
now racked up very slowly the object will come dimly into view. In
most cases a good view can be obtained with a low power without
using the finer adjustment, but if there is any difficulty the fine adjust-
ment can be used.

72 BOTANY FOR BEGINNERS CHAP.

With a high power the method of finding the focus is the same,
only greater care is required. If the £ objective is used, it can be
racked down until the image of the objective appears to meet the
objective when the specimen is nearly in focus. If the tube is gently
racked away from the slide it will come into view, and with the finer
adjustment the focus can be found.

The pupil must on no account rack the tube towards the object at the
same time he is looking down it. If this is done the object may be
missed and the objective may be forced through the slide. The section
may in this way be damaged and the lens ruined. The best way is to
look at the objective until it is nearly close to the object, and then,
while looking down the tube, rack it away until the object becomes clear.

(4) An object should always be examined with the low power first,
and after all possible detail has been made out with this, the high power
can be used.

(5) A high power must never be used unless the object is covered
with a cover-glass. This prevents the mounting media from touching
the objective.

(6) Drawings should always be made of the objects examined. This
practice compels attention to details, and tends to produce the habit of
close observation. In drawing, a fine pointed pencil should be used,
and the drawings made either on good cartridge paper or Bristol board.
The drawings should always be made to scale.

SUMMARY.

Sections of a plant can oe made in three directions. If the section of
the stem is made at right angles to its long axis it is called a transverse
section. When the section is made in the direction of the long axis of
the stem and passes through the organic centre, it is a radial longi
tudinal section. If the section passes lengthwise through the stem but
does not pass through the organic centre, it is said to be a tangential
longitudinal section.

Mounting Specimens. — Fresh specimens can be mounted in water,
and material which has been preserved in alcohol must be mounted in
either alcohol or glycerine. Sections must be kept wet to prevent air
bubbles from forming. Cleanliness is necessary if good work is to be
done.

Hand-Lens. — A hand-lens is a piece of glass which possesses the
property of magnifying objects, and is mounted in wood, horn, or metal
for protection and use. To use such a lens it is necessary to hold it
close to the eye and to bring the object into such a position that it can
best be seen.

Cells. — Plants are built up of elements which receive the name of
cells. A cell is surrounded with a cell-wall, and contains protoplasm.

Tissues are formed by the union of a number of cells. There are
three kinds of tissues ; they are-
Epidermal tissue ;
Vascular tissue ;
Ground tissue.

vi HOW TO PREPARE AND EXAMINE SECTIONS 73

The Compound Microscope is an instrument which consists of lens
and accessory parts. Such an instrument is used for the examination of
the minute parts of plants.

QUESTIONS ON CHAPTER VI.

(1) What do you understand by the term " section''? What kinds
of sections can be made from a stem ?

(2) Write a set of rules to guide you in mounting sections.

(3) Why, in mounting sections, must a cover-glass be placed over the
object ; and how is such a cover glass put on ?

(4) Explain what is meant by air-bubbles, and how they find their
way into sections.

(5) A hand-lens and a transparent section are given to you. How
should the lens be used so as to examine the section?

(6) What is a cell ? Of what parts does a cell consist ?

(7) A Tomato is given to you to make a preparation showing the
cells. Explain how you would proceed to do this.

(8) Explain what is meant by the term "tissue." What kinds of
tissue can be found in plants ?

(9) Give an account of the structure of the stem of the Sunflower,
and compare it with the stem of the Maize.

(10) Explain the term annual ring, as applied to woody trees. How-
is it that each ring is formed of a light coloured layer and a dark coloured
layer ?

CHAPTER VII

THE HISTOLOGY OF THE CELL

The Cell. — All parts of plants agree in being built up or
microscopic elements which have received the name of cells (p. 65).
The cells which are present in a woody plant, such as the Oak,
may be living or dead. ^Head-cells perform an important func-
tion in giving firmness and .rigidity to the plant. They may
also conduct water from the roots to the leaves, and protect the
deeper parts of the plant from injury. Cells may be separate,
as in the ripe pulp of the Tomato, but in most cases they are
united to form a tissue. Cells vary very much in form and
development, and upon this will depend the kinds of tissue
which they may produce. It will be an advantage to begin by
studying the individual cell.

The Structure of a Cell.— As living cells change with
age it will be better to take a young cell and to follow it until it

becomes mature.
P In a young cell,

such as can be seen
in the cortical (p.
66) tissue of the
stem of most
plants, the follow-
ing three principal
constituents can be
distinguished. On
the outside a mem-
brane separates the cell from others which surround it, and
is called a cell- wall. In close contact with the whole surface
of the cell-wall, and filling the entire cavity of the cell, is the
protoplasm. Embedded in the protoplasm is a . denser
granular portion which is called the nucleus.

FIG. 101. — The left-hand. figure, a young parenchyma
cell; the right-hand figure, an older cell. CW,
cell-wall ; P, Protoplasm ; N , nucleus ; N L,
nucleolus ; V, vacuoles.

THE HISTOLOGY OF THE CELL

Formation and Growth of the Cell- Wall.— The cell-
wall is very strong and elastic, and is formed from and by the proto-
plasm, and its increase in thickness and area depends upon the
vital activity of such protoplasm. The cell-wall may grow in area
owing to the stretching caused by the pressure set up inside
the cell, but throughout this increase -in size new material is
deposited to strengthen it. In
some cases the stretched cell-
wall breaks, and the ruptured
edges separate. The break is
commonly repaired by the
deposition of a plug of new
material which connects the
disconnected surfaces.

The cell-wall grows in thick-
ness by the deposition of suc-
cessive layers on the internal
surface of the first-formed layer.
This kind of growth is termed
growth by apposition. The
subsequent growth of the cell-
wall by the deposition of new
material between the old is
called growth by intussuscep-
tion. As a general rule growth
in thickness does not take place

until after a cell has reached its full size. When such a cell-wall
is examined "by the high power of the microscope, it exhibits a
stratified appearance; this is owing to the constituent layers
acting on the light differently. All the markings which are
found on cell-walls are due to the unequal deposition of the new
material during growth in thickness. The spiral, annular, and
pitted walls, for example, which are found inThe wood of most
plants, are caused by this unequal growth.

The Chemical Composition of the Cell Wall.— If a
few cells be treated with iodine-stain 1 the cell-wall will assume
a yellow colour, and the further addition of a single drop of

1 Iodine-stain is made by dissolving crystals of potassium iodide in distilled water
until a strong solution is made and then adding crystals of iodine. If this is diluted
with distilled water to the colour of brown sherry it is ready for use. The alcoholic
solution is made in the same way, only alcohol is used instead of water.

FIG. 102.— Cell with thickened wall.
in, middle lamella ; t, pit ; 7f ,
pitted transverse wall. ( X 300.) (S.)

76 BOTANY FOR BEGINNERS CHAP.

strong sulphuric acid causes the yellow colour to be replaced by
a deep blue.

This reaction is characteristic of a substance termed cellulose.
We may consequently conclude that the cell-wall consists
principally of such cellulose. Cellulose consists of three
chemical elements, known as carbon, hydrogen, and oxygen.
All organic bodies which have the hydrogen and oxygen
present in that proportion in which these elements are present
to form water are grouped together as carbohydrates. The
proportion by weight in which carbon, hydrogen, and oxygen
are present in cellulose is represented by the following percentage
composition : —

Carbon 44-44

Hydrogen . 6' 17

Oxygen 49'38

99.99 (= 100 very nearly.)

From this it will be seen that there is eight times as much
oxygen as hydrogen by weight in cellulose.

But water is made up of eight parts by weight of oxygen to
one of hydrogen, as the following analysis shows : —

Hydrogen 11*136

Oxygen 88*864

lOO'OOO

Hence, we are justified in classing cellulose as a 'carbo-
hydrate.

Mineral substances such as silica, carbonate of lime, and
compounds of iron are also found deposited in cell-walls.

Chemical Changes which the Cell-wall may under-
go.— i. A portion, or all, of the cell-wall may become cuti-
cularised. This is caused either by a change in the
cellulose, or by the deposition of cutin in the cell-wall.

The epidermal cells of some leaves afford a good example of
cuticularisation. If a section of a leaf of the Rhododendron be
touched with iodine and sulphuric acid, some of the layers of
the wall of the epidermal cells will assume a deep blue colour ;
the colour is deepest in the inner layers, the outer layers not

vii THE HISTOLOGY OF THE CELL 77

showing it at all. The external layer of the epidermal cells is
called cuticle, which is almost impermeable to water.

The walls of corky cells have the same properties as cuti-
cularised cell-walls, and they give the same reaction with iodine.
The corky walls consist of a substance called suberin. Both
cutin and suberin contain about 74 per cent of Carbon.

2.— The cellulose of the cell-wall may, owing to the deposition
of lignin in the wall, become lignified. A lignified wall gives
a blue colour when treated with aniline chloride and hydro-
chloric acid. Lignification, while it makes the cell-wall harder
and more elastic, does not prevent water being able to readily
traverse it. Lignification takes place most largely in woody
tissue, and to a less extent in other parts of the plant.

3.— In some cases the cell-wall may become more or less
mucilaginous. This change is caused by the conversion of
cellulose into mucilage, which may be either a form of cellulose
or a form of gum.

EXPT. 70. — Obtain a small quantity of Spirogyra, which is found in
ditches and ponds during summer. Mount some of it in water, and
examine it under a low power of the microscope. . Note —

(i) That the filament is surrounded by a cell-wall.

(ii) That each cell contains protoplasm.

(iii) That a nucleus is present in the protoplasm.

Place a small quantity of Spirogyra in a watch glass and cover it
with iodine solution. Mount it in water and examine it first with a low
power, then with a high power. Note —

(i) The cell-wall is but slightly stained yellow.

(ii) The protoplasm is coloured a deeper yellow or brown.

(iii) The nucleus is still more deeply stained than the protoplasm.

EXPT. 71. — Take a Date stone and scrape away the brown coat.
Cut sections from the reserve material (which is cellulose) stored up in
the seed. This can be done by using either the heel of the razor or a
strong knife. Mount a thin section in glycerine, and examine first
under a low power and then under a high power. Note —

(i) The thick cell-walls with a number of thin places called pits in
them ; the membrane which closes those pits is called the closing
membrane, and is, in reality, the primary cell- wall. For this reason
the closing membrane is sometimes called the middle lamella (Fig. 102).

(ii) The granular protoplasm.

(iii) Soak a section for a few minutes in iodine, and mount in
glycerine. The cell- wall is stained slightly yellow.

(iv) Mount another section which has been soaked in iodine and a
drop of strong sulphuric acid. Examine it under a low power only.
Observe how the cell-walls swell, lose their sharp outline, and assume

BOTANY FOR BEGINNERS

CHAP.

(See that no sulphuric acid finds its way on to the

a blue colour,
microscope).

EXPT. 72. — Take some cotton wool and first soak it in alcohol for
half an hour to drive out the air. Mount it in water. Examine it first
under a low power, then under a high power. Note-^

(i) The twisted filaments, which consist of single cells.

(ii) The thick colourless cell-walls.

(iii) The remains of the protoplasm seen clinging to the interior of
the cell-walls.

(iv) Treat a small quantity with iodine solution — the walls stain
slightly yellow.

(v) Add a drop of strong sulphuric acid after the cover-glass has been
removed, when a distinct blue colour will be seen.

Evidently cotton consists principally of cellulose.

FIG. 103. — Section of endosperm
of Date. (X 400.)

FIG. 104. — Cotton
fibres. '

FIG. 105. — Longi-
tudinal section
of a Match,
showing pits.

EXPT. 73. — Cut sections from a cork and soak them in alcohol.
Mount the thinnest in water and examine with the microscope.
Observe : —

(i) The cell-walls, which have a clear outline. The cells have lost
their contents.

(ii) Treat another section with iodine solution, the walls stain yellow.

(iii) Treat another section with iodine and sulphuric acid, the walls
stain yellow or brown, not blue ; neither do they swell with sulphuric
acid, but keep their outline.

EXPT. 74. — Cut sections from a wooden match and soak them in
alcohol to remove the air bubbles. Mount a thin one in glycerine, and
observe the cell-walls, which are seen to have a number of pits (Fig. 105).

(i) Treat a section with iodine ; it stains yellow.

(ii) Treat another section with iodine and sulphuric acid ; it swells
and stains brown.

NOTE. — A cellulose wall can thus be distinguished from a lignified
or a corky wall because it gives a blue colour with iodine and sulphuric

THE HISTOLOGY OF THE .CELL 79

acid. A lignified wall is stained brown and swells, and a corky wall is
stained brown but does not swell.

EXPT. 75.— Soak some Linseed seeds in water, and note how they
swell. The outer layers of the seed, which were hard and horny, have
been converted into mucilage.

Make a section from a dry seed and mount in glycerine and water.
Examine with a low power, and notice the wall swells and the
striations on it become very clear.

The Protoplasm.— The protoplasm is the living and active
part of the cell. It is a semi -solid material, which has embedded
in it a number of granules, and is kept moist by the cell-sap,
which saturates the wnole of the cell.

It is probable that the protoplasm consists of a number of
fibres which cross in all directions to form a net-work, the
meshes of which are filled in with a more fluid substance.

In living cells the protoplasm is always in close contact with
the cell-wall ; but if the temperature of the cells be raised to
120° F, the protoplasm coagulates, i.e., sets like the white of an
egg when boiled. In this state it loses all power of movement
and dies. Alcohol or weak acids produce similar result.

The Composition of Protoplasm.— If a few cells are
treated with iodine, the protoplasm is coloured brown. This
is the same colour which the substances called proteids give with
iodine, and it seems very probable that protoplasm is built up of
proteids.

A proteid is a substance which contains Carbon. Hydrogen, Oxygen,
Nitrogen, and Sulphur. The essential element of a proteid is nitrogen,
and in some cases the name nitrogenous substance is used in place of
proteid. The proportion of the above elements in living protoplasm
is not known. If an analysis is made of protoplasm it is necessary to
kill it in the process, and there may be a difference between the com-
position of living and dead protoplasm. Protoplasm certainly contains
the same elements which are found in proteids. It is the most wonder-
ful substance in the universe, because life is never found apart from it.
There appears to be no difference between the protoplasm of plants and
that of animals.

The Movement of Protoplasm.— The protoplasm of a
plant cell possesses the power of movement. These movements
can be observed in large cells with thin and transparent walls,
especially when the colourless protoplasm contains a large
number of granules. These granules are driven backwards and
forwards with the stream, and they appear much as particles of

8o BOTANY FOR BEGINNERS CHAP.

mud would do in a swiftly moving river. When the granules in
their movements go round and round the interior of the cell,
the movement is called rotation.

In an old cell where the protoplasm does not completely fill
the interior of the cell the spaces are termed vacuoles.
Vacuoles are filled with cell-sap. The connection between the
protoplasm in different parts of the cell is kept up by strands
of protoplasm. In such a cell the granules move up one
strand and down another, much as the blood corpuscles move
in the blood stream. This latter movement, which is more
complex than that of rotation is called circulation. The indi-
vidual granules in the current can be seen to move with
unequal rapidity, according to their sizes, the smallest moving
fastest.

The currents in the protoplasm are apparently irregular, now
advancing, now retreating, sometimes suddenly arrested, and
commencing again with increased rapidity. The movements
depend upon temperature. In winter, during frost, and in
summer, during dry weather, they are arrested. In spring,
when there is plenty of moisture and a fair amount of heat, they
are seen at their best.

EXPT. 76. — Obtain a plant of the American Water 'Weed (Elodea]
and mount a single leaf in water. Place a cover-glass on, and examine
wMi a high power. Note —

(i) The cells and the granules in the protoplasm.

(ii) The movement of the granules ; they move round and round—
this is rotation.

(Hi) Gently"warm the slide over hot water. Examine again. The
temperature being raised the granules move faster.

(iv) Now hold the slide either over a gas flame or a spirit lamp until
the water boils. Examine again. There is no movement, the protoplasm
has been killed.

EXPT. 77. — Remove a portion of the epidermis of a Stinging Nettle
and mount it in water ; examine with the low power. Notice —

(i) The hairs ; focus one in the centre of the field and, using the high
power, observe —

(ii) The cell is wider at the base than at the apex of the hair;
examine the protoplasm, nucleus, vacuoles, and cell-wall.

(iii) The granules are seen in a state of motion ; they move up one of
the strands and down another — this is circulation.

EXPT. 78. — Remove a small portion from near the core of an American
Apple. Mount in water and examine under a low power ; fogus a cell

VII

THE HISTOLOGY OF THE CELL 81

near the centre of the field and proceed to observe a single cell with the
high power. Make out —

(i) The cell-wall, protoplasm, nucleus, and vacuoles>

(ii) Treat with iodine solution ; the protoplasm is stained brown, and
the nucleus a very dark brown.

(iii) Treat a freshly prepared specimen with salt solution (2\ per cent. ).
The wall retains its original position and appearance, but the protoplasm
contracts and leaves the walls. This is known as plasjnolysis.

(iv) Wash out the salt solution with water and 'exainlne again ; the
protoplasm slowly regains its original position.

The contraction of the protoplasm is due to the salt solution
attracting the water from the cell ; and it regains its original
position when water again is taken in.

The Nucleus. — The nucleus is a denser portion of the proto-
plasm ; it stains a deeper colour when treated with iodine
solution. In shape the nucleus is somewhat oval, and in its
interior a distinct rounded body called a nucleohts may be pre^
sent. It is built up of proteids, and contains a large quantity of
phosphorus. A nucleus is present in all cells, and this seems to
show that the presence of such a body is necessary to the life of
the cell. It is always formed from a preceding nucleus. The
exact function of the nucleus is not known, but in every case of
cell-production the nucleus divides first. It has been suggested
that the nucleus is the most important part of the cell, and that
it forms the protoplasm which surrounds it.

The Difference between a Young and Mature
Cell. — A very young cell is completely filled with protoplasm.
As the cell increases in size the cell-wall grows faster than the
protoplasm, causing cavities, which become filled with cell-sap,
to appear in it. These cavities are called vacuoles, which in a
very old cell may be very large.

The Contents of the Cell.— The cell always contains a
number of other substances in addition to the protoplasm and
the nucleus. In fact, at one time or another, it contains every
element that the plant contains, for the puatoplasm is the active
material of the cell, and produces all the organic substances
found in the plant. The vacuoles and all parts of the cell are
saturated with cell-sap. The protoplasm contains granules,
which, according to their nature, are variously known as chloro-
plasts, leucoplasts, and chromoplasts. Starch and Aleurone
grains are also found in cells, while fats and, in some cases,
crystals of calcium oxalate may be present.

82 BOTANY FOR BEGINNERS CHAP.

The Cell-Sap is the watery fluid which saturates the proto-
plasm and the cell-wall, and also occupies the vacuoles ; it con-
sists of water which holds in solution a number of organic and
inorganic substances. The substances in solution are either on
their way to be built up into protoplasm, or have themselves
been formed by previously existing protoplasm. The organic
substances present in cell-sap are sugar, organic acids, proteids,
and in many cells colouring matter. The inorganic substances
are chlorides and sulphates of potassium and sodium. Solid
bodies, in addition to these dissolved substances, may also be
present in the vacuole, e.g., starch grains, aleurone grains, and
raphides or needle-like crystals of calcium oxalate.

Chloroplasts. — In the cells building up the green parts of
plants a green colouring matter is present called chlorophyll.
In all the higher plants the chlorophyll is found in the form of
granules known by various names, as chlorophyll grains, chloro-
phyll corpuscles, or chloroplasts. A chloroplast is a small
mass of protcplasm saturated with chlorophyll. This is shown
to be the case when a cell which contains chloroplasts is treated
with alcohol. The chlorophyll is dissolved out, and colourless
grains are left behind 7~these are called leucoplasts.

It is only in those cells which are exposed to light that
chlorophyll is developed. The conditions necessary for the
development of chlorophyll, are : —

(a) a certain temperature, a few degrees above the freezing
point ;

(b] light ; any light will do if it is only intense enough ;

(t) a small quantity of iron in the food of the plant. The
necessity of iron for the development of chlorophyll is very
interesting, for no iron is found in the chlorophyll itself. The
iron is probably necessary in the chemical changes which result
in the formation of chlorophyll.

From what has been said about light being necessary for the
formation of chlorophyll, it will be understood why it is found
only in the surface cells. The important function of chlorophyll,
which can only be exercised in the presence of light, is to absorb
the carbon dioxide in the atmosphere, and to split it up into
carbon and oxygen. The oxygen is returned to the air, but the
carbon combines with the elements of water to form sugar

VII

THE HISTOLOGY OF THE CELL

which is eventually converted into starch. The starch grains
are formed inside the chloroplasts.

Chloroplasts ultimately undergo decay, when, as in the case
of frilling leaves, all that is left of them are a few yellow granules.
During autumn the nutritive matters in the cells of the leaves
are carried to other parts of the plant to be stored up for future

FIG. 106. — Epidermis from under side of a leaf of Iris, showing chloroplasts.
A, surface view ; B, in transverse section ; s, stoma ; a, air cavity ; f, depression ;
c, cuticle. (X 240.) (S.)

use ; and with these nutritive materials the greater part of the
chloroplasts are removed. In the Copper Beech the chlorophyll
is masked by colouring matter, which is dissolved in the
cell-sap.

Leucoplasts. — In those cells not exposed to light, colourless
granules are found ; these are called leucoplasts. Leucoplasts
may IDC converted into chloroplasts if the cell in which they are
present is exposed to light. The change of colour which a
Potato may undergo when exposed to light is owing to some of

G 2

BOTANY FOR BEGINNERS

CHAP.

the leucoplasts being concerted into chloroplasts. The leuco-
plasts perform the important work of converting sugar into
starch. The starch grains are produced on the outside of the
leucoplasts, not inside as in the chloroplasts. They are of

a denser consistency than
chloroplasts, and somewhat
flattened in shape. Qhr$mo-
plasts are masses of proto-
ptesm which are saturated
with colouring matters other
than chlorophyll.

FIG. 107.— Leucoplasts. A, C, D, E,
viewed from side ; B, from above ;
E, one changing colour. (X54O.) (S.J

FIG. 108. — Cells from pulp of Tomato,
showing chromoplasts.

EXPT. 79. — Cut a thin section from a Beetroot, and mount it in
water. Examine under a low power. Note —

(i) The large cells with their thin cell-walls.

(ii) The protoplasm which lines the cell-wall.

(iii) The coloured cell-sap which does not escape from uninjured
cells.

(iv) Dip a fresh section in alcohol for half a minute, before examin-
inc* it. The coloured sap oozes out because the protoplasm has been
killed.

EXPT. 80. — Obtain a few Fern Prothalli from a gardener. Mount
a small one in water, and examine with a low power. Note —

(i) The cells crowded with chlorophyll corpuscles.

(ii) Many of the chlorophyll corpuscles are undergoing division, as
is shown by their shape. Grains shaped like an hour glass are under-
going division.

(iii) Place a prothallus in a watch glass and cover with alcohol, and
leave it for half an hour. Mount and examine. Note — The colouring
matter has been dissolved out of the corpuscles, but they still retain
their outline.

THE HISTOLOGY OF THE CELL

EXPT. 81. — Sow a few mustard seeds in two plant pots ; keep the
soil moist ; place one in a dark place and the other in a light place.
Observe from day to day. Note —

The stems and leaves of those plants kept in the dark are far longer
than those grown in the light, but they are pale yellow or dirty white in
colour.

Those grown in the light are bright
green. Light is necessary for the de-
velopment of chlorophyll,

EXPT. 82. — Obtain a few young
Potatoes and cut them into slices. Place
them in a weak solution of picric acid
for a day or two. Wash the solution
out with a weak solution of alcohol, and
harden the slices in a 70 per cent, solu-
tion of alcohol. Cut sections from near
the surface, and stain them in alcohol
and iodine solution. Mount in glycerine,
and examine under a high power.
Note—

(i) Some of the granules in the protoplasm stain blue. These are
starch grains.

(ii) Attached to some of the starch grains small yellowish bodies may
be seen ; these are leucoplasts.

Leucoplasts may be seen in colourless tissue in which starch
is being stored up. Underground tubers and rhizomes contain
them,

Starch Grains. — Chloroplasts in those cells which are
exposed to light always contain starch grains. In many
cases the starch grain is so large "that the chloroplast only

FIG. 109. — Cells from prothallus
of Fern. (20.)

FIG. no. — Starch grains of Wheat.
A, large ; B, small grains.
(X54o.) (S.)

FIG. in. — Starch grains of' Oat?.
A, compound grains ; B, isolated
grains. (X540.) (S.)

surrounds it as a thin covering. Chloroplasts are always form-
ing starch at the expense of the sugar which is produced by
the constructive activity of the chlorophyll and the protoplasm.
In the green parts of plants starch grains are very small because

BOTANY FOR BEGINNERS

CHAP.

they are always undergoing a change due to the action of a
ferment found in the cells. This ferment, which is called
diastase, reconverts the starch into sugar. Large starch grains
are only found in those parts of plants where they are stored
up for future use. Each plant produces a starch_grain which
.differs in shape and size from the grains produced by other
plants. By making use of this fact, adulterations of foods can
be detected under the microscope.

Starch grains are always striated. The organic centre of the
grain around which it grows by the deposition of new material
is termed the hilum. The hilum is pro-
duced by the activity of either the chloro-
plast or the leucoplast, and the successive
layers which are deposited are also due to
the same activity. Starch grains grow in
the same way that a cell-wall grows in
thickness, that is, by apposition or by
intussusception. In some cases compound
grains may be found in cells. These can be
divided into two kinds, (a) those called
spurious, which are produced by two or
more grains coming together and uniting
as a result of pressure, (b) true compound
grains which are produced by the same
leucoplast, and round which there are
always a number of layers which bind the
grains together.

Starch grains can always be detected in

cells by treating them with iodine solution, when they give a
deep-blue colour. They thus differ from cellulose which only
gives a yellow colour with iodine.

Starch is a carbohydrate having the same composition as
cellulose but differing in its physical properties. When treated
with potash solution starch swells up, and if boiled with
water will form a paste. If heated while dry, starch is converted
into dextrine and becomes soluble.

Aleurone Grains.— Aleurone grains, or as they are some-
times called, proteid grains, are found in many seeds. Each
aleurone grain Is built up of a crystalloid and a globoid.
The crystalloid is composed of albumen or proteids, and a

FIG. 112. — Starch
grains from seed-
leaves of Bean.
(X 540.) (S.)

VII

THE HISTOLOGY OF THE CELL

FIG. 113. — A, cell from the endosperm of the Castor
Oil plant ; B, aleurone grains ; g, glcboid ; k,
crystalloid. (.X 540.) (S.)

globoid is formed of a double phosphate of lime and magnesia.

If a section of a Castor Oil seed be made and examined by the

high power of the

microscope, the

aleurone grains

will be seen to be

embedded in the

protoplasm, which

is also rich in oil.

The proteids are

stored up in plants

principally in the

form of aleurone

grains. They are

large in oily seeds

but small in starchy

seeds.

The crystalloids
are sometimes
found free. The
crystalloids differ
from mineral crys-
tals because they
swell up if treated
with various re-
agents.

Fats.— Drops of
oil are found in the
protoplasm in the
cells of many
plants. These
drops are very nu-
merous in the case
of the seeds of the
Castor Oil plant,

Rape, Flax, and in the fruit of the Olive. The non- nitrogenous
substances stored up as reserve material in the above plants
occur as drops of oil. When the seeds germinate the fat is
converted into sugar.

Raphides. —In most plants crystals of calcium oxalate are

FIG. 114.— Section of grain of Wheat. /, pericarp ; /,
seed coat ; al, aleurone grains ; am, starch grains ;
n, cell nucleus.

BOTANY FOR BEGINNERS

CHAP.

found. They are always found in vacuoles, and when needle-
shaped are called raphides. In many monocotyledonous plants
they protect the plant from snails, slugs, &c.

Sugars. — Various kinds of sugars and
allied bodies are found in the cell-sap. The
principal forms of sugar thus found are
grape-sugar and cane-sugar. Grape-
sugar is found in the fruit of tile Grape, and
Cane-sugar is found in the Sugar-cane and
Beetroot.

EXPT. 83. — Scrape a freshly cut surface of a
Potato tuber with a knife, and mount the
scrapings in water. Examine first with a low
power and afterwards with a high power. Note —

(i) The numerous starch grains which appear
very bright. Observe the hilum and the stratified
appearance of each grain.

(ii) Run some iodine solution under the cover-
glass by holding a piece of blotting paper at one
edge of it, and placing a drop of the solution on
the other edge. The paper soaks up the water,
and the solution takes its place. The iodine stains
the starch grains blue.

(iii) Treat another preparation with chlor-zinc-
iodine,1 which is an acid solution of iodine. The
starch grains stain blue, but they also swell up and
lose their bright appearance.

(iv) To a fresh preparation add potash solution.
The grains swell.

EXPT. 84.— Cut a section from the Potato tuber
and mount in water, examine with a high power
and find

(i) A spurious compound grain,
(ii) A true compound grain.

EXPT. 85. — Obtain a few Castor Oil seeds, and expose the pearly
endosperm or reserve material by removing the outer covering. Cut a
thin section of the endosperm and mount in olive oil. Examine with
ths high power. Note —

(i) The aleurone grains or proteids granules,
(ii) Find the crystalloid and globoid in the grain.
EXPT. 86. — Cut sections from a cotyledon of the Almond, and mount
in water.

Observe the bright-looking drops in the water ; they are oil drops.

1 Chlor-zinc-Iodine (Schulze's solution) consists of a mixture of zinc dissolved in
pure hydrochloric acid, and a small quantity of potassium iodide dissolved in water.
It is an acid solution of iodine.

Fii. 115.— Cell, with a
bundle of Raphides.
(X 160.) (S.)

VII

THE HISTOLOGY OF THE CELL

Formation of New Cells.— It is necessary that new
cells should be produced so as to ensure growth and also to
continue the life of the plant. The mode in which new cells
are produced will depend upon
the kinds of organs in which the

FIG. 117. — Diagram to
illustrate cell division.

FIG. 1 16.— Starch grains from Potato. The left-hand figure shows a spurious
compound grain ; the middle a true compound grain ; and the right-hand, figure
ordinary starch grains.

division takes place. Cell-formation goes on in two different
sets of organs, viz., vegetative and reproductive.

The vegetative parts of a plant are those portions which
arc of service to the life of the individual, such as root, stem,
branches and leaves. The method of
cell-formation in all these organs is by
simple division. In this case the nu-
cleus first divides into two, the protoplasm
then separates into two parts, and a cell-
wall is formed between the newly formed
nuclei. Two cells are thus formed. These
cells are at first only half the size of the

parent cell, but they grow and become as large as the cell from
which they were formed. In this method of cell formation
there is only a portion of the cell-wall of the new cell which is
new, the remaining portions belonging to the parent cell.

The reproductive parts of a plant are those portions which
are concerned in the propagation of the species. They are a
tax on the individual which bears them, for such individual
must find the whole of the material necessary to give the off-
spring a start in life. In all the higher plants this is done by
the production of seeds, which produce new individuals, and so
keep up the continuity of the species. Cell-formation in
reproductive organs is characterised by a rounding off of the
protoplasm : and no portion of the parent cell-wall aids in the
formation of new daughter cells.

90 BOTANY FOR BEGINNERS CHAP.

The parent cell contains a nucleus, which, as before divides
into two, and each part again divides, and thus there are four
nuclei in the cell. The protoplasm now divides into four masses
and each portion arranges itself around a nucleus. Each
rounded portion of protoplasm produces a new cell-wall and the
mother wall disappears, liberating the four cells. This method
of cell formation is called free-cell formation, and it only
takes place in reproductive organs.

SUMMARY

The Cell. — All parts of plants are built up of microscopic elements
called cells, which may be living or dead.
The Structure of a Cell. — Each living cell consists of —

(1) The cell-ivall, built up of cellulose.

(2) The protoplasm , which lines the cell-wall.

(3) The nucleus^ a denser portion of the protoplasm.

Changes which the Cell- wall undergoes. — It may become — (i)
Cuticularised, (2) Lignified, (3) Mucilaginous.

Protoplasm. — The protoplasm is the living portion of the cell. It
contains the elements carbon, hydrogen, oxygen, nitrogen, and sulphur.
Protoplasm possesses the power of movement. It may rotate or
circulate.

The Nucleus.— All cells possess a nucleus, and in it a mtclcolus may
be present. It is built up of protoplasm, and contains a large quantity
of phosphorus.

The Contents of the Cell. — The cell may contain —

Cell-sap. Starch grains.

Chloroplasts. Aleurone grains.

Leucoplasts.
Chromoplasts.

Fats.

Crystals.

Chloroplasts are masses of protoplasm containing a green colouring
matter called chlorophyll. The conditions necessary for the production
of chlorophyll are —

1 i ) A certain intensity of light.

(2) A temperature above the freezing point.

(3) A small quantity of iron in the food.
The functions of the Chloroplasts are —

1 i ) To absorb carbon dioxide from the air.

(2) To split up the carbon dioxide into carbon and oxygen.

(3) To form starch from sugar.

Leucoplasts are masses of colourless protoplasm. They form starch
in those parts of the plants not exposed to light.

Chromoplasts are masses of protoplasm saturated with other colouring
matter than chlorophyll.

Starch Grains are formed (i) by chloroplasts in organs exposed to

vii THE HISTOLOGY OF THE CELL 91

light, (2) by leucoplasts in the underground stems, roots, &c. Starch
grains grow by apposition and intussusception.

The hilum forms the organic centre of the grain. Successive layers
are deposited round the hilum, thus giving the grain a stratified appear-
ance. A ferment (diastase) can convert starch into sugar. Starch
grains may be simple, spuriously compound, or truly compound.

Composition of Starch. — It is built up of the same elements as
cellulose. It is a carbohydrate.

Aleurone Grains. — The proteids found in plants are stored up as
aleurone grains and proteid crystals. Each aleurone grain consists of a
crystalloid and a globoid.

Formation of New Cells. — New cells are produced by (i) simple cell
division, (2) free-cell formation. The former method takes place in
vegetative organs, the latter in reproductive organs.

QUESTIONS ON CHAPTER VII

(1) Describe the structure of a young cell, and explain how it differs
from a full-grown cell.

(2) How is the cell-wall formed, and how does it grow in thickness ?

(3) To what are the markings due which can be found in cell-walls?

(4) Give an account of the composition and properties of cellulose.

(5) Describe the structure of a living parenchymatous plant cell.
What chemical elements enter into the composition (a) of the cell-wall,
(b) of the protoplasm ?

(6) How can you distinguish by the aid of the microscope a cellulose
wall from (a) a lignified wall, (b) a corky wall, (c) a mucilaginous wall?

(7) What is protoplasm ? What do you know about the properties
of protoplasm ?

(8) What is meant by the circulation of protoplasm?

(9) Enumerate and give a brief account of the most important sub-
stances which are found in cells.

(10) What is a chloroplast ? Where are chloroplasts found? What
work can they perform which makes them useful to the plant ?

(n) Give an account of the conditions which are necessary for the
development of chlorophyll.

(12) What is a leucoplast? How may a leucoplast be converted
into a chloroplast ? Why are leucoplasts said to be starch builders ?

(13) What is the nature of starch? How is it formed, and what are
its uses ?

(14) To what substance do the green parts of plants owe their colour ?
State and explain the nature of the work which green parts of plants are
alone able to perform.

(15) What is an aleurone grain ? Where are aleurone grains found ?

(16) How are new cells formed ? What kinds of cell-formations are
there ?

(17) Explain clearly how starch is formed in a Potato, and from what
source it is derived. (1899.)

CHAPTER VIII

THE HISTOLOGY OF THE TISSUES

Kinds of Cells.— All cells can be classed according to their
shape into (a) Parenchyma, and (b) Prosenchyma.

A parenchyma cell is one in which the diameter of the cell
is about the same in every direction. Cells of this description
are especially abundant in the succu-
lent parts of plants. The ground tissue
of a plant is composed of parenchyma
cells, and in many cases they form a
storehouse for reserve material, as in
the turnip. When such cells are very
numerous in an organ they are said to
form parenchymatous
tissue.

A prosenchyma
cell is long and nar-
row. Cells of this
description may lose
their living contents

and become filled with air and water. If a
number of prosenchyma cells are placed end-to-
end so that the transverse walls are at right
angles to the long side walls, the transverse
walls may become perforated, and so form a
vessel. The living contents of the cells be-
come absorbed after the transverse walls are
broken down, and eventually the fully formed vessels contain
only air or water. The markings on the walls of the vessels
supply the botanist with their characteristic names.

FIG. 118. — Parenchyma cell
from fruit of Bean. ( X 500.)

FIG. no.— Dia-
gram of Prosen-
chyma cell.

CH. vin THE HISTOLOGY OF THE TISSUES

20. — Pitted, spiral, annular,
and reticulate vessels.

If the walls are pitted (p. 78) they are called pitted- vessels.
When the thickenings of the walls appear to form a spiral, the
vessels are spoken of as spiral
(Fig. 120). When the markings
give to the vessel a reticulate or
netted appearance, such vessels are
termed reticulate (Fig. 120). If
the transverse walls have been per-
forated by a single round opening
while the rest of the walls remain
to form thick rings the vessels are
called annular. Vessels of the
above kinds are found in the wood p,G>
of all plants. The walls of all such
vessels are lignified.

Sieve Tubes. — In the formation of the sieve vessels or
sieve tubes the transverse walls are not completely broken
down, but they are perforated by fine canals through which the
protoplasm passes — for such vessels keep their living contents.

The wall which contains
the perforations is called
a sieve plate. In some
plants the longitudinal
walls may become simi-
larly perforated so that
sieve plates are also
formed there. The walls
of sieve tubes are always
unlignified, and the ves-
sels contain a watery cell-
sap. In close contact
with the sieve tubes, and
formed from the same
cells during development,
long narrow cells are

formed, and these are called companion cells. The nuclei
of the sieve tubes are broken up and disappear, but the com-
panion cells keep both their protoplasm and nuclei.

Kinds of Tissues. — When a number of cells are intimately
connected, and perform the same kinds of work, they are

FIG. 121. — Parts of sieve tubes from Vegetable
Marrow. A, surface view of sieve plate ;
B, C, longitudinal sections, showing sieve
plates ; D, contents of sieve tube ; S, com-
panion cells ; PA, protoplasm ; C, lateral
sieve plate. (X 270.) (After Strasburger.)

BOTANY FOR BEGINNERS

CHAP.

spoken of as forming a tissue. In the higher plants there are
three kinds of tissue systems, they are called epidermal
tissue, vascular tissue, and ground tissue. The above
tissues may be primary or secondary. Primary tissues are
formed from the growing cells of the embryo, and the secondary
tissues from those new layers of growing cells which are formed
from the embryonic cells.

EPIDERMAL TISSUE

Epidermal Tissue.— Those cells which cover the plant
and protect the deeper parts from injury, form the epidermis.

FIG. 122. — Surface view of the epidermis from FIG. 123. — Surface view of the
underside of leaf of Balsam, showing stomata. epidermis of the Dog's

(X 160.) (S.) Mercury. (X 300.) (S.)

As a rule the epidermis is only one cell in thickness, and the
cells do not contain any chlorophyll. The protoplasm of the
epidermal cells is reduced to a very thin layer which lines the
cell-walls, and the cavities of the cells contain a colourless cell-
sap. The outer wall of the epidermal cells forms a cuticle, which
protects the deeper tissue from a too rapid loss of water.

Stomata are found in the epidermis of all those parts of
plants which are exposed to the air. Each stoma is a minute
opening between two cells which contain chlorophyll and are
called guard-cells. The stoma is formed by a young epider-
mal cell becoming divided by a septum into two equal cells.

VIII

THE HISTOLOGY OF THE TISSUES

FIG. 124. — Diagram illustrating
formation of stoma. i, young
epidermal cell ; 2, division of
cell ; 3, the cell-wall split to
form the stoma.

The septum then splits open, the opening constitutes the stoma,

and the cells form the guard-cells. The size of the stoma

depends upon the movement of the guard-cells. The stomata

are found on all the green parts of plants, but they are most

numerous on the under side of the
leaves. If both sides of a leaf are
alike, the stomata will be equally
developed on both the upper and
lower surfaces. In those plants
with floating leaves the stomata
are found on the upper side only.
Stomata can open and shut by
the change in the shape of the

guard-cells. The interchange of gases between the interior of

the plant and the external atmosphere — froin which interchange

the plant obtains energy and food material — goes on through

the stomata, which also give out watery vapour.

Some plants have openings in the epidermis by which they

give out water in a liquid state. Such openings are called

w a t e r-p ores.

The water - pores

are larger than the

stomata and are

always open.
Hairs. — From

the epidermis hairs

are produced (a) for

protection (b} for

the nutrition of the

plant. When the

hair consists of a

single cell it is said

to be unicellular ;

if a number of cells

enter into the com-
position of a single

hair it is termed

a multicellular

hair. The former are found on the roots of plants, where

they take in water containing minerals in solution. The latter

FIG. 125.— Waterpore, with a portion of epidermis
from a leaf. (X 240.) (S.)

BOTANY FOR BEGINNERS

CHAP.

are found on the stem, leaves, and flowers of most plants.

The unicellular root -hair is produced by the outgrowth of an

epidermal cell.

On the surface of the stinging nettle a very large number of

hairs are produced. If one is examined by the microscope it is

seen to consist of a single cell at the apex ; the base of this cell
is fixed in a number of cells which be-
long to the epidermis. The tip of the
hair of a stinging nettle is strengthened
with silica, while the rest of the hair con-
tains carbonate of lime. In the ter-
minal cell a poisonous fluid is produced.
When an animal touches the plant the
stiff pointed hairs enter its skin and the
poisonous fluid is poured into the wound.
The well known smarting sensation
which a person feels when "nettled" is
due to this acid fluid. The well known
method of rubbing the wound with a
Dock leaf is to neutralise the acid with
the alkaline secretion present in the
Dock leaf.

Emergences. — Emergences are
modified portions of the epidermis
which may act as glands. A gland
is an organ which secretes some sub-
stance from the materials which are
brought to it in the cell sap. The ten-
tacles of the Sundew are well known
examples. These secrete a substance
very much like the gastric juice of the
higher animals, and this secretion en-
ables the plant to digest any insects
which the plant may catch.

EXPT. 87.— Cut sections from a Turnip or
from a Potato ; mount the thinnest in water.
Note—

(i) The shape of the cells. They are
parenchyma cells.

(ii) The contents of the cells. These consist principally of
protoplasm and starch grains.

FIG. 126.— Stinging hair
cf Nettle. (X6o.) (S.)

vin THE HISTOLOGY OF THE TISSUES 97

EXPT. 88. — Obtain either the stem of the Pumpkin or of the
Cucumber ; harden in alcohol. Cut either radial or tangential longi-
tudinal sections. Stain in iodine solution,
and mount a few in glycerine. Note —

(i) The sieve tubes, the transverse walls of
which are clearly seen owing to the substance
which surrounds them being stained dark
brown, the wall only staining faintly yellow.

The substance which surrounds the sieve
plates is called callus, and it is probably com-
posed of cellulose. The amount of callus
present will depend upon the age of the sieve
tubes, and the season of the year.

(ii) The protoplasm which lines the tubes
and is well developed just over the sieve-
plates.

(iii) The shape of the sieve tubes.

(iv) The companion cells. These are long
and narrow and their nuclei can be clearly
seen under the high power.

EXPT. 89. — From the lower side of the leaf
of the Wallflower pull off a small portion of
the epidermis ; this can be done by raising
the epidermis with a knife and gently pulling
at it ; as a rule the edge of the piece of
epidermis will be thin enough for examination.
Mount in water, and examine it with the high
power. Note —

(i) The sinuous outline of the cell-wall.

(ii) The spindle-shaped hairs which lie close
to the surface of the leaf.

(iii) The stomata, which are very numerous.
Each stoma is surrounded by a pair of sausage-
shaped cells — the guard-cells.

EXPT. 90.— Strip from the underside of the FlG 127._Digestive
leaf of the Hyacinth (the leaf of any mono- gland of the Sun-

cotyledonous plant will do as well) a small dew- (x6o.) (S.)

portion of the epidermis. Mount in water and
examine first under a low power, then with the high power. Note —

(i) The epidermal cells.

(ii) The stomata, which are very large and numerous.

Strip from the upper surface of the leaf a piece of epidermis and treat
in the same way.

(iii) Compare its appearance with the lower epidermis and note in
what ways they agree and how they differ.

EXPT. 91. — Mount in water the rootof a germinating Mustard Seed ;
examine it under a low power. Note —

(i) The root-hairs ; these are unicellular, and are formed by the out-
growth of the cells of the apidermis.

98 BOTANY FOR BEGINNERS CHAP.

(ii) To some of the root-hairs particles of soil adhere.
This adhesion of the root-hairs to particles of soil is due to the con-
version of the outer layer of the cell-walls into mucilage.

EXPT. 92. — Pull off a small piece of the epidermis of a leaf of the
Sunflower ; mount in water, and examine under a low power. Note —

The multicellular hairs which are scattered over the surface of the
leaf.

VASCULAR TISSUE.

Vascular tissue.— If a skeleton leaf be examined it will be
found to consist of a number of hard fibres ; these are the vas-
cular bundles. These bundles form the conductive tissue of
the plant, that is, they conduct water from the roots up the
stem, to the leaves, and the elaborated sap from the leaves to
those parts of the plant which need it. Such bundles are also
the principal supporting tissue of the plant and form the frame-
work upon which the softer parts are fixed. The bundles always
resist decay longer than the other parts of the plant, and in a
skeleton leaf or stem are the only parts present. In the higher
plants there are two principal types of vascular bundles, they are
known as open and closed bundles. Open bundles are found in
Dicotyledonous plants and closed bundles in Monocotyledonous
plants.

Structure of Bundles. — If a vascular bundle of the
Dicotyledonous type be examined under the microscope, there
will be seen : —

(1) The Xylem, which is nearest the centre of the plant.

(2) The Phloem, which is always the portion of the bundle
most removed from the centre of the plant.

(3) The Cambium, which lies between the xylem and
phloem.

Xylem. — The xylem is the woody portion of the bundle, and
in the vascular bundle of the stem it is always found nearest to
the pith. It consists of a number of vessels and parenchyma
cells. The vessels which are- found in the xylem are spiral
(p. 93), annular (p. 93), reticulated (p. 93), and pitted (p. 93).
The spiral vessels are the nearest to the pith, then come the annular
vessels, and these two kinds together make up the first-formed
xylem, called protoxylem. The reticulate vessels come
next, and the pitted vessels are to be found close up to the
Cambium. Scattered about among the vessels, fibrous cells are
to be found. These fibrous cells are long and narrow, and in

vin THE HISTOLOGY OF THE TISSUES 99

some cases have sharp-pointed ends. Prosenchyma cells are
also found mixed up with the vessels (p. 92).

In addition to the vessels and the fibrous cells a number of
parenchyma cells occur mixed with the vessels ; these paren-
chyma cells never fuse together.

Phloem. — The phloem consists of two portions which are
known as the soft- and hard-bast. The soft bast is found
close to the cambium and consists of sieve tubes, companion
cells, and parenchyma cells. The sieve tubes (p. 93) are long
vessels which have their transverse walls perforated. Com-
panion cells — which can always be recognised in a longitudinal
section of the bast because they are long narrow cells rilled
with protoplasm, and each possessing a large nucleus — are
found with the sieve-tubes. In transverse sections companion
cells appear as if they were originally cut off from the same cells
as the sieve-tubes. Mixed up with the sieve-tubes and com-
panion cells a few parenchyma cells may be found ; these are
known as phloem parenchyma.

The hard bast is composed principally of bast fibres, which
are long narrow spindle-shaped fibres, much like the fibres of
wood. Parenchyma cells are to be found mixed with the bast
fibres.

Cambium. — The cambium is found between the xylem and
phloem. It consists of cells which do not as yet show the
characters of either xylem or phloem. Those cambium cells
nearest to the phloem pass gradually into it, while those nearest
the xylem eventually become the xylem. The cells near the
middle of the cambium are thin walled, and contain protoplasm.
They are in a state of constant division, and thus form new
cells. The new cells on one side pass into and form new
xylem. Similarly, on the other side new phloem is produced.
A tissue composed of cells which can divide in this way is
called meristematic, because it is capable of dividing up
and producing new cells.

Open and Closed Vascular Bundles.— Those vascular
bundles which possess a cambium are said to be open because
they can produce new tissue. If the bundles consist of xylem
and phloem only, without a cambium, they are termed closed
bundles, because growth in thickness of the bundle cannot go
on. When the xylem and phloem are in contact on one side
only, they are said to be collateral.

H 2

100

BOTANY FOR BEGINNERS

CHAP.

The general arrangement of the elements in an open vascular
bundle is shown below in a tabular form.

Near Pith.

Reticulate vessels
Pitted vessels . .

Cambium cells. .

Sieve-tubes
Companion cells

Bast fibres

I | Soft bast .
Hard bast.

Xylem

Cambium

Phloem.

Open Vascular
Bundle.

Bundle Sheath (PericycJe. )

The Monocotyledonous Type of Vascular Bundle.—
If a vascular bundle of a monocotyledonous plant be examined,
there will be found two kinds of tissue present. They are :—

(1) The Xylem, which always points towards the centre of
the stem.

(2) The Phloem, which is turned towards the exterior of the
stem.

The structure of such a vascular bundle is much the same as
in the dicotyledonous type, only the variety of vessels is not so
great. The bundle is surrounded by a special sheath of thick
walled cells.

The Course of Vascular Bundles.— If the bundle passes
from the stem into the leaf, as most bundles do, it is called a
common bundle, because it is common to both stem and
leaf. The portion of the bundle in the leaf is termed a leaf-
trace. In a few cases the bundle never passes from the stem,
and it is then spoken of as a cauline bundle.

The arrangement of the bundles in the stem depends upon
the phyllotaxis (p. 36). If the arrangement of the leaves
is |, the bundle which proceeds from the leaf will pass
through five internodes before it joins on to the bundle below,
as in the Wallflower.

If the leaves are decussate there will be four rows of leaves
on the stem, and the bundle from any leaf will have to pass
through two internodes only before it joins on to the bundle of
the leaf below. Thus, the bundle which proceeds from a leaf
will pass inwards for a short distance, then bend and pass down

viii THE HISTOLOGY OF THE TISSUES 101

the stem until it joins on to the bundle below. The above are
the arrangements in most dicotyledonous plants.

The course of the bundles in monocotyledonous plants is very
irregular. The bundles from any leaf base pass into the stem
towards the centre, then bend back and pass for some distance
down the stem, when they join on to the bundles below.

EXPT. 93. — Obtain a piece of the stem of the Wallflower with a
number of leaves on it, and trace out the course of the vascular bundles.
To do this bisect it longitudinally so as to pass through the middle of a
leaf ; clear away the pith with a blunt knife. Note —

(i) That the bundle which enters the stem from the midrib of the leaf
runs inwards for a short distance, then turns straight downwards, and
ioins on to the leaf vertically below the first leaf.

(ii) That the bundle runs through five internodes without joining a
bundle.

(iii) That there are two smaller bundles that act in the same way.

(iv) That in any section of the stem of the Wallflower there must be
five large bundles and ten small bundles cut through.

EXPT. 94.— Trace the course of the vascular bundles in the stem of
the Deadnettle. Bisect the stem longitudinally, so as to pass through
two leaves on the same side of the stem. Clear the pith away, and
note —

(i) That the bundle which enters the stem runs inwards and then
downwards, and joins on to the bundle of the leaf vertically below.

(ii) That the bundle only passes through two internodes before it
joins on to the bundle below.

(iii) That in the stem of the Deadnettle there are four main vascular
bundles, which correspond to the decussate arrangement of the leaves.

THE GROUND TISSUE.

The Ground Tissue.— The tissue which is found in the
centre of a stem and between the vascular bundles and the
epidermis is called ground or fundamental tissue. It
usually forms the principal part of the primary tissue of the
plant, and can be arranged in three groups : —

The Pith within the ring of vascular tissue.

The Cortex between the ring of bundles and the epidermis.

The Medullary rays between the pairs of bundles.

The vascular bundles seem to be fixed in the ground tissue,
which in a young stem appears to surround them. It may
contain chlorophyll and be used for obtaining food.

While the epidermal tissue protects the internal parts of the
plant and the vascular bundles perform the office of conduction
and support, the ground tissue provides for the nutrition of the
plant and forms a store for reserve material.

102 BOTANY FOR BEGINNERS CHAP, vin

SUMMARY.

Parenchyma cells are those in which the diameter is about the same
in all directions.

Prosenchyma cells are long and narrow.

Vessels are formed by the perforation of the transverse walls of cells
which are placed end to end. The following are very common : —
Spiral vessels. Reticulate vessels.

Annular vessels. Pitted vessels.

Sieve tubes are formed from cells which have their transverse walls
perforated to form sieve plates.

Tissues. — There are three tissue systems in a plant, viz. : —

Epidermal tissue, which covers and protects the deeper parts of

the plant from injury.
Vascular tissue, which forms the supporting and conducting tissue

of the plant.
Ground tissue, which fills in the spaces between the epidermal and

vascular tissue.

Stomata are the small openings which are found between guard -cells
in the epidermis of the aerial parts of plants.

Hairs may be either unicellular or multicellular. They may protect
the plant from insect pests, or be used for taking in food.

Vascular bundles may be closed or open. If the bundle is open it
will consist of ( I ) Xylem ; (2) Cambium ; (3) Phloem.

If the bundle is closed it will consist of (i) Xylem, and (2) Phloem.
The Course of Vascular Bundles depends upon the arrangement
of the leaves on the stem.

QUESTIONS ON CHAPTER VIII.

1 i ) How does a parenchyma cell differ from a prosenchyma cell ?

(2) What is a vessel? How are vessels formed? Enumerate the
different kinds which are found in wood.

(3) In what respects of structure and function do the vessels of the
bast (sieve tubes) differ from those of the wood ? (1892.)

(4) Describe fully the structure of a vascular bundle in the stem of a
dicotyledon. Explain how such a bundle differs from that of a mono.-
cotyledon. (1894.)

(5) What is a stoma? On what parts of the plant are the stomata
chiefly developed ? How is a stoma formed ?

(6) Give an account of the structure of the epidermis of a leat.

(7) What is a vascular bundle ? Of what parts does it consist ? (1898. )

(8) What is the cambium ? Explain where you would find it in the
trunk of a tree, and what its importance is? (1898.)

(9) Describe the structure of a young parenchyma cell, and explain
how it differs from that of a full-grown cell of the same kind. (1892.)

(10) Explain what is meant by ground tissue. In what parts of a
plant is ground tissue found ?

(u) Give a short account of the longitudinal course of the vascular
bundle in a dicotyledonous plant.

(12) What kinds of hairs are found on plants? Of what use to the
plant are hairs ?

CHAPTER IX

THE HISTOLOGY OF THE SHOOT AND ROOT

The Structure of a Dicotyledonous Stem.— A trans-
verse section of a young dicotyledonous stem, when examined
under the low power of the
microscope, shows the follow-
ing parts (Fig. 128). Exter-
nally the section is limited by
a single layer of cells, many
of which may produce hairs ;
this is the epidermis. Inside
the epidermis comes the cor-
tex, bounded on the inside by
a single row of cells called
the endodefmis. Inside
the endodermis a broken ring
of vascular bundles is found,
which is surrounded on the
outside by a layer of cells,

known as the pericycle/ The vascular bundles are divided from
one another by a number of cells forming medullary rays.
The centre of the stem is full of loose cells which form the pith.

FIG. 128. — Transverse section of young
stem of Sunflower, showing ten sepa-
rate vascular bundles in the ground
tissues. Ef>, epidermis ; co, cortex ;
Pi, pith ; Pit, phloem ; cb, cambium ;
xy, xylem.

Outside.
Epidermis .
Cortex . . \
Endodermis j
Pericycle . \
Phloem . . \
Cambium . I
Xylem . . I
Pith ....

Inside.

Epidermal Tissue
Ground Tissue .

Vascular Tissue
Ground Tissue

Transverse
Section of
Dicotyledonous
Stem.

104

BOTANY FOR BEGINNERS

CHAP.

In an old stem of the Sunflower the vascular bundles form a
complete ring, and in such an old stem a complete ring of cam-
bium passes through the bundles and across the medullary rays.
Those parts of this cambium ring which lie between the vascular
bundles are spoken of as forming the
interfascicular cambium (p. 99).
The interfascicular cambium is formed
by the cells between the bundles be-
coming meristematic, i.e., they begin
to divide up and so complete the ring.
This portion of the cambium ring forms

FIG. 129. — Transverse section of older stem of Sun-
flower, showing the first formation of interfascicular
cambium. Ph. and cb, phloem and cambium ; xy>
xylem ; Scl, sclerenchyma ; s, spiral vessels ; sf,
interfascicular cambium.

FIG. 130. — Transverse sec-
tion of part of cylinder of
old Sunflower stem ; Ph,
phloem ; cb, cambium ;
xy, xylem ; WF, wood
fibres ; MR, medullary
rays \v, vessels of xylem.

vascular elements which partly fill up the spaces between the
bundles. The whole of the cambium during the active period
of growth produces xylem on one side and phloem on the other.
Thus, in an old stem the vascular cylinder is formed (p. 66).

EXPT. 95.— Cut transverse sections of a young stem of the Wallflower
and mount in water. Look for a thin section, and note —

(i) The epidermis, a single row of cells which surrounds the cortex.

(ii) The cut ends of the vascular bundles.

(iii) The ground tissue forming the cortex and pith.

ix THE HISTOLOGY OF THE SHOOT AND ROOT 105

EXPT. 96. — Transfer the thinnest section observed in Expt. 95 to
alcohol, and let it remain for twenty minutes to bleach it. Now stain
it with iodine solution, mount in glycerine, and examine a vascular
bundle under the high power. Note —

(i) The endodermis, a single layer of cells containing starch. The
starch grains stain blue.

(ii) The pericycle, a layer of cells inside the endodmeris.

-xy.

FIG. 131. — Diagram of old stem of Sunflower as seen in transverse section, showing
an almost complete cylinder of secondary tissues, interrupted by medullary rays.
(x 6.) Ep, epidermis \ co, cortex; Scl, sclerenchyma patches; Ph, phloem;
cb, cambium ; jry, xylem ; Pi, pith.

(iii) The phloem inside the pericycle ; the transverse walls of the sieve
tubes will be stained yellow, and the perforations through which the
strands of protoplasm pass may be stained brown.

(iv) The cambium, several layers of cells inside the phloem.

(v) The xylem between the cambium and pith. This can be easily
recognised by the large cavities of the vessels.

(vi) The pith, which fills the interior of the stem.

EXPT. 97. — Select a very young stem of the Sunflower. This can
be obtained by germinating seeds, and planting out the young plants in
plant pots. The stem should not be more than £th of an inch in

106 BOTANY FOR BEGINNERS CHAP.

diameter. Cut transverse sections and mount in water. Examine
under a low power. Note —

(i) The epidermis.

(ii) The cortex.

(iii) The vascular bundles, which are not united.

(iv) The ground tissue between the bundles.

(v) The cambium, between the phloem and xylein.

EXPT. 98. — Cut transverse sections from a stem of the Sunflower,
which is twice the age of the stem used in Expt. 97, and mount in
glycerine. Observe —
(i) The vascular bundles,
(ii) The cambium ; see if a complete
ring is formed.

EXPT. 99. — Prepare a thin transverse
section from the stem of a full-grown Sun-
flower, which has been kept in spirit for
some time to remove the resin and air,
and to harden the tissues. Mount in
rb glycerine or glycerine jelly. Examine
under a low power, and note —

(i) The vascular cylinder, which is
formed by the union of the bundles.

FIG. 132.— Transverse section (ii) The pith, the cells of which have
of young stem of Wallflower. lost their living contents.

vtsculafbundles^C^coAet; («*) The large multicellular hairs which
E, epidermis ; A, hair. project from the epidermis.

EXPT. ioo. — Cut a radial longitudinal

section of the stem of the Wallflower, and mount in water. Examine
first under a low power then under a high power, and note —

(i) The epidermis. (v) The phloem.

(ii) The cortex. (vi) The cambium,

(iii) The endodermis. (vii) The xyleni.

(iv) The pericycle. (viii) The pith.

Growth in thickness of a Dicotyledonous Stem.—
In those perennial plants which possess open vascular bundles
new additions are made to both the xylem and the phloem by
the cambium which is between them. The xylem increases in
size by additions to its outer surface, the phloem by additions to
its inner surface, the central portion of the cambium remaining
meristematic. Thus, every season new layers are produced,
but far more xylem is formed than phloem. The rings
which are seen in a cross section of the oak are produced

IX THE HISTOLOGY OF THE SHOOT AND ROOT 107

by the action of the cambium and each ring marks a years
growth.

Each annual ring consists of a dark coloured layer and a
light coloured layer. In spring, . when the active period of
growth commences, the pressure on the cambium is very little,
because during the winter the bark and cortex have been
ruptured by the action of frost and changes in temperature.
The cambium is able to produce large cells and vessels which
are thin- walled, thus a light coloured layer is formed. During
spring the ruptures
in the bark are re-
paired, and as the
season advances,
more and more
pressure is brought
to bear on the cam-
bium, and smaller
and thick - walled
cells and vessels
are formed. These
are dark in colour
because they con-
tain less air, and
thus a dark colour-
ed layer is formed.
The age of a tree

can be told by its annual rings, and if the rings are examined
and compared the size of the layers will give us some clue to
the kind of season when any ring was produced.

The Formation of Periderm.— In those plants which
grow in thickness the epidermis is replaced by a new tissue
which receives the name of periderm. The periderm is
formed from the pericycle, which divides up into a number of
rows of cells ; one of these rows forms the phellogen or cork
cambium. The phellogen produces new cells on both its
inner and outer surfaces ; the cells on the inside keep their
living contents and form the phelloderm ; those on the outside
lose their living contents and their cellulose walls are converted
into cork. The cork cells are impervious to water, and so cut
off the supply of water to the cortex and epidermis ; these con-

FIG. 133. — Section of Larch stem ; showing annual rings.

io8

BOTANY FOR BEGINNERS

CHAP.

sequently dry up and aid in the formation of bark. The parts
which form bark and periderm are shown below : —

{Phelloderm
Phellogen
Cork cells

Bark.

Cork cells
Endodermis
Cortex
Epidermis

The primary phellogen after a time ceases its activity, and a
deeper phellogen is formed. Still later, even this may discontinue

FIG. 134. — Transverse section through
stem of Maple. D, dried up epi-
dermis and cortex ; C, 'cork cells ;
PH, phloem ; XY, xylem. (X 150.)

FIG. 135.— L, Lenticel from the stem of
the Lilac. (X25«) PD, phellogen ;
PL, phelloderm ; E, epidermis.

its function, until at last the new phellogens which are produced
come to be formed in secondary bast. If the bark which is
produced by these deeper phellogens is thrown off in scales
it is called Scaly bark ; this is found on the Pine and Plane
tree. On the other hand, if the secondary bark forms complete
rings which are concentric — ringed bark is formed, as in
the Honeysuckle, Clematis, and Grape-vine.

Lenticels. — In the Periderm are produced small _ pores
called lenticels. They are developed just beneath those places
where the stomata existed in the epidermis. They are openings
formed by the phellogen, which produces cells between which
intercellular spaces are formed (Fig. 135).

EXPT. 101. — Prepare sections of the flower stem of the White Lily,
and if the stem is fresh, mount the thinnest section in water ; if the
material has been in spirit, mount in glycerine. Observe —

(i) The epidermis, a single layer of cells.

IX THE HISTOLOGY OF THE SHOOT AND ROOT 109

(ii) The cortex, which is several layers of cells in thickness,
(iii) The pericycle, which is very strong and forms a thick ring,
(iv) The scattered vascular bundles, which are embedded in the ground
tissue.

EXPT. 102.— Cut a transverse section of a two-year-old stem of the
Wallflower. Mount in water, and examine under a low power.
Note—

(i) The periderm, which is formed from the pericycle.

(ii) The bark, which is outside the phellogen or cork cambium.

The Structure of a Monocotyledonous Stem.— If a
transverse section of a young stem of the Maize be made and
examined by a low power the
following parts will be seen,
Fig. 136. On the outside an
epidermis which consists of
a single layer of cells. Im-
mediately inside this, a broad
band of thick-walled paren-
chyma forms the cortex. The
cortex is a mechanical tissue
and is the principal support
of the plant. The remain-
ing part of the stem is made
up of scattered vascular
bundles and ground tissue.
TJiere is r^ rprnhinm anrl

FIG. 136. — A portion of a transverse section
of stem of Maize, (x 20.) E, epi-
dermis ; C, cortex ; VB, vascular
bundles.

no_£rr»wth jn thickness ran take place a

result of tria

division of the cambium ring.

Structure of a Dicotyledonous Root.— If a transverse
section of a very young tap-root of the Wallflower is examined
the structure appears very different to that of the stem. On
the outside the piliferous layer is formed ; this is another name
for the young epidermis of the root. Many of the cells of the
piliferous layer are converted into root-hairs, hence the name.
A root-hair is unicellular and is produced from a single cell of
the epidermis. Inside the epidermis, and limited internally
as in the stem by the endodermis, is the cortex. The centre of
the root is occupied by a vascular cylinder which consists of two
masses of xylem and two masses of phloem. The xylem masses
alternate? with the phloem masses. In the stem the protoxylem

no BOTANY FOR BEGINNERS CHAP.

points towards the pith^ in the root it points toward the cortex.
The vascular cylinder is surrounded by the pericycle.
Outside.

Piliferous layer with root hairs , . \

Cortex (parenchyma cells) . . . . I

Endodermis (single layer of cells). . \ Transverse section of

Pericycle (single layer of cells) . . ; Dicotyledonous Root.

Phloem masses\(In wallflower two, j

Xylem masses /which alternate) . . /
Inside.

Growth in Thickness of the Root.— The roots of dico-
tyledonous plants in which the stem increases in thickness
themselves also grow in thickness. The growth in thickness
of roots depends, as in stems, upon the cambium. The cam-
bium, see Fig. 128, passes on the outside of the xylem, and on
the inside of the phloem. As growth goes on the structure of
the root becomes more and more like the stem, until in an old
stem it is very difficult to distinguish the two. Periderm is also
formed in a root from the pericycle ; this cuts off the cortex,
and the root may be smaller after the second year of growth
than during the first year.

The Structure of a Monocotyledonous Root.— In
the root of a monocotyledonous plant there is a large central
cylinder which contains, as a general rule, a larger number of
distinct bundles of wood and bast. In some roots there may be
as many as twelve alternating masses of xylem and phloem.
The structure is essentially the same, but because the cambium
layer is absent, there is no growth in thickness.

Expf. 103. — Select a young root of the Wallflower, and cut a thin
transverse section from it, and mount in water. Examine under a low
power. Note —

(i) The piliferous layer with its root-hairs.

(ii) The cortex, which is several layers of cells in thickness.

(iii) The endodermis, which is a single layer of cells surrounding the
pericycle.

(iv) The pericycle, just within the endodermis.

(v) The alternating masses of phloem and xylem.

There are only two vascular bundles present.

EX.PT. 104. — Obtain a bulb of the Hyacinth, and from one of the
adventitious roots cut a thin transverse section, mount in water.
Examine under a low power. Note —

(i) The central cylinder, which is limited by the endodermis and the
pericycle.

(ii) The very numerous masses of xylem and phloem, which also show
the alternating arrangement already seen in the Wallflower.

ix THE HISTOLOGY OF THE SHOOT AND ROOT tti

The Structure of the Leaf.— Each leaf consists of the
three tissue systems, but by far the largest portion is ground-
tissue. The whole of the leaf is covered by the epidermis, and
between the upper and lower epidermis comes the Mesophyll.
Fig. 138. The mesophyll is built up of palisade cells above,
and spongy parenchyma below. Between the spongy paren-
chyma and the palisade tissue the vascular bundles run; these
bring sap from the root to the cells of the leaf, and carry away
the elaborated sap. The palisade tissue consists of regular,
fairly elongated cells, which contain a very large number of
chloroplasts, and only a few intercellular spaces. The spongy

H ,US ,UE

LS/

FIG. 137. — Transverse section of young
root of Wallflower. {After Scott.)
P, phloem ; X, xylem ; C, cortex ; P1,
piliferous layer ; R, root hair.

FIG.

38. — Transverse section of leaf of
Rhododendron. (X 250.) US, upper
side of leaf ; LS, lower side of leaf ;
P, palisade parenchyma ; S, spongy
parenchyma ; VB, vascular bundle ;
E, epidermis ; H, hypoderm.

parenchyma forms a loose tissue full of intercellular spaces.
The cells of this tissue are not so well supplied with chloroplasts.
The intercellular spaces of the leaf communicate with the
stomata, so that any gas which may enter the stomata finds its
way into the deeper parts of the leaf. The outside of the epi-
dermis of the leaf is always of the nature of cuticle.

EXPT. 105. — Place a piece of the leaf of the Wallflower between
little slabs of carrot, and with a sharp razor cut slices right across.
Separate the transverse sections of the leaf so obtained in water in a

112

BOTANY FOR BEGINNERS

CHAP.

watch glass. With a camel's hair brush mount the thinnest one in
water, and examine first with a low power then with the high power.
Note—

(i) The upper epidermis, a single layer of cells with an outer cuticle.

(ii) The palisade parenchyma, which consists of cells, cylindrical in
form, with a few air spaces between them ; the chloroplasts are very
numerous in the cells.

(iii) The spongy parenchyma, which consists of loosely-arranged
irregular cells with large air spaces between.

(iv) The lower epidermis with the stomata. Each stoma opens into
a large intercellular space — the air chamber.

(v) That each stoma is a small opening between two guard-cells.
Each guard cell is sausage-shaped and curved, the ends of the guard-
cells being firmly joined together.

(vi) The vascular bundles have the xylem above and \h& phloem below.
The xylem ends in the palisade cells and the phloem in the spongy
parenchyma.

(vii) That the guard-cells contain chloroplasts, and that the other
epidermal cells have no chloroplasts.

The Growing Point of the Shoot.— The growing point
of the shoot consists of several layers of cells, which are meris-
tematic in character. These cells are
rich in protoplasm, and possess large
nuclei, and are in a constant state of
activity, i.e., growing and dividing
to form new cells. From this meri-
stem all the new tissues of the shoot
are developed. There are three
distinct layers of cells at the apex,
viz. : —

(i.) Dermatogen.— On the outer
FIG. 139.— Diagram of the grow- portion of the growing point a single
mftoglnn;0f FR^W^em"; layer of cells is present. These divide
PL, plerome. ' Up by walls being formed at right

angles to their surface. This layer

gives rise to the epidermis of the young shoot, and is called
the dermatogen.

(2.) Periblem. — Below the dermatogen a layer of cells is
found, which, at the apex, may be only one layer of cells thick, but
lower down may be several cells thick. This is the periblem or
young cortex, for it forms the cortex.

(3.) Plerome. — Underneath the periblem is found a group
of cells, which gives rise to the whole of the vascular cylinder of

ix THE HISTOLOGY OF THE SHOOT AND ROOT 113

the stem, including the pith, the bundles, and pericycle. This
layer receives the name oi plerome.

Formation of Leaves. — Leaves are formed from the der-
matogen and periblem. The dermatogen grows out and the
periblem follows. From the dermatogen the epidermis only is
formed, the mesophyll and vascular bundles being formed from
the periblem.

Formation of Branches.— When a branch arises in the
axil of a leaf, it is formed from the dermatogen and periblem,
the plerome taking no part in it. Thus a branch is produced
from the outer tissues of the stem, />., from the cortex and
epidermis, and it is said to be formed exogenously.

The Growing Point of the Root.— All the new tissues of
the root are produced from its apex. Though there are no

FIG. 140. — A transverse section of the
stem of Ivy ; showing origin of aerial
root. (X 8.)

FIG. 141.— Root cap of Barley.
(Magnified.)

leaves to be developed, there is a root-cap to form. If the young
root of a Bean plant is held up to the light, two parts can be
distinguished, a lighter outer portion and a darker inner portion.
The outer portion is the root-cap, and the inner dark zone the
growing point, which is protected by the root-cap. The growing
point consists of three layers, as in the shoot. They are : —

(i.) The plerome, which forms the vascular cylinder.

(2.) The periblem, which forms the cortex,

\ \

114

BOTANY FOR BEGINNERS

CHAP.

FIG. 1^2. — Diagram of growing
point of root. RC, root -cap ;
K, apex of growing point ; D,
calyptrogen ; PR, periblem ;
PL, plerome.

(3.) The calyptrogen (which is another name for dermatogen)
forms the piliferous layer and the root-cap. Cells are cut- off

from the outside of the calyptrogen
to form the root-cap. The root-cap
by coining in contact with the sharp
fragments in the soil protects the
growing point from injury. It is
worn away as it passes through the
soil, and is repaired by the produc-
tion of new cells by the calyptrogen.
Formation of Branches.—
The branches of the root are pro-
duced from the pericycle, or outer
layer of the vascular cylinder. In
the stem, as we have seen, the
branches arise from the periblem
and dermatogen, but in the root
the whole of the branch is formed

from the plerome. The branches of the root are said to be
endogenously formed. When the young root is formed it
has to force and eat its way through the cortex and the piliferous
layer in order to reach the soil.

SUMMARY.

A Dicotyledonous Stem. — In a dicotyledonous stem the following
parts are present, beginning on the outside —

(i) Epidermis ; (2) cortex ; (3) endodermis ; (4) pericycle ; (5)
phloem ; (6) cambium ; (7) xylem ; (8) pith.

Growth in Thickness of a Dicotyledonous Stem. — A woody tree
shows annual rings of growth which are produced by the activity of the
cambium forming new xylem. Each ring consists of a dark coloured
and a light coloured portion. The latter is produced in spring, the
former in autumn.

Periderm is formed from the pericycle. The pericycle divides up and
forms the phellogen or cork cambium , which forms on the inside a layer
of cells which keep their living contents, and an outer ring of cells
which lose their living contents. The former is called the phelloderm,
and the latter the cork-layer.

Lenticels are openings found in the periderm.

A Monocotyledonous Stem differs from a dicotyledonous stem in
having the vascular bundles scattered, and in no growth in thickness
taking place.

Boots differ from stems in having alternating masses of phloem and

ix THE HISTOLOGY OF THE SHOOT AND ROOT 115

xylem. Dicotyledonous roots grow in thickness by a cambium which
forms new xylem and phloem. A monocotyledonous root only differs
from that of a dicotyledon in having more masses of xylem and phloem
and no secondary growth.

Leaves are outgrowths of the stem, and consist of —

(i) An upper epidermis; (2) palisade tissue; (3) vascular bundles;
(4) spongy parenchyma : (5) lower epidermis with stomata.

Growing Point of Stem. — There are three layers of cells in the grow-
ing point of the stem, viz., (a) Dermatogen, which forms the epidermis ;
(b) Peribkm, which forms the cortex ; (c) Plerome, which forms the
vascular bundles and pith.

Growing Point of Root. — In the root there are three layers of cells
from which all parts of the root are formed — (a) Plerome, which forms
the vascular cylinder ; (b) Perible/n, which forms the cortex ; (c) Calyp-
trogen, which forms the piliferous layer and root-cap.

QUESTIONS ON CHAPTER IX.

(1) Describe the way in which the stem of a dicotyledonous tree
grows in thickness, and explain how it is that its wood shows annual
rings. (1889.)

(2) Compare the structure of the stem of a monocotyledonous plant
with the structure of the stem of a dicotyledonous plant.

(3) Describe the structure of an ordinary foliage-leaf as seen in
transverse section.

(4) Explain how periderm is formed. How does periderm differ
from bark ?

(5) What is a medullary ray? What is meant by primary and
secondary medullary rays ?

(6) Describe the structure of the growing point of the stem, and con-
trast it with that of the root. (1897.)

(7) What is cambium ? What is its position in the stem of dicotyle-
donous plants, and what is its use ? (1890 T. )

(8) Explain exactly how the root and the stem of any dicotyledonous
plant differ from each other in structure, as seen in transverse section
under the microscope.

(9) How does the branching of the stem differ from the branching of
the root ?

(10) How can the longitudinal course of the vascular bundles in any
stem be determined ?

(u) What is a lenticel? On what parts of a plant are lenticels
found ?

(12) Describe the structure of the stem in any monocotyledon, as
seen in longitudinal and in transverse sections.

(13) Briefly describe the chief anatomical differences between the
stem of a monocotyledon and that of a dicotyledon. (1891 T. )

(14) The stem of an oak tree continues to grow in thickness so long
as the tree lives, whereas the stem of a palm tree does not grow any
thicker when once formed. Explain the cause of this difference.

I 2

J;. CHAPTER X

THE PHYSIOLOGY OF NUTRITION

Physiology. — That division of botany which investigates
the work which plants can perform is called physiology.
Physiology shows us how each structure is adapted to the
functions which a plant, or organs of a plant, can perform. In
simple plants like Protococcus — which grows on walls, trunks of
trees, and can live if it is only damp,— the entire body of the
plant consists of a single cell, which performs all the work
necessary both for the life of the plant and for the reproduction
of its kind. In most multicellular plants, as we have seen, the
constituent cells differ very much in structure, and this difference
of structure is connected with the performance of some particular
function.

In all the higher plants we obtain what is known as division
of labour. Each special part of the plant has some special
work to perform. The roots collect water and minerals ; the
leaves take in carbon dioxide ; the stem conducts the water
from the roots to the leaves ; and the leaves from these materials
form sugar, starch, cellulose, and proteids.

The striking attributes which especially characterise plants as
living bodies, and by which they can be distinguished from non-
living bodies, are (i) that from time to time food is taken in and
the plant grows, (ii) movements are carried out by the plant
for its benefit, (iii) certain parts of the plant are separated, and
these parts produce new individuals, z.e., reproduction takes
place.

Nutrition. — Those processes which go on in a plant and
by which it is able to form new material from the constituents

CH. x THE PHYSIOLOGY OF NUTRITION 117

of its food are spoken of as nutrition. The nourishment of the
plant can only go on where food materials are taken in and so
changed that they can become a part of the plant. If the food-
supply is not kept up the death of the plant is a foregone
conclusion. Growth can only go on where the food-supply is in
excess of that demanded for the production of the energy
expended during its present activity.

The Composition of Plants. — The most abundant in-
gredient in a living plant is water. Many succulent plants, such
as Turnips and Cabbages, contain more than 90 per cent, of water.
Timber which is felled during the driest season of the year
seldom contains less than 40 per cent, of water. If a plant is
dried at a temperature of from 230° F. to 248° F. all water is
expelled and the solid matter alone remains.

The solid matter of a plant can easily be made to burn, and
the greater part will disappear in the form of gas, a white ash
only being left behind. If the gases which are given off during
the combustion of the solid matter of a plant are collected and
examined, they are found to consist of carbon dioxide, water,
ammonia, and a compound of sulphur. If these compounds are
split up into their elements they are found to consist of Carbon,
Hydrogen, Oxygen, Nitrogen, and Sulphur.

Without these five elements no plant can be produced, and
they are called the combustible elements of the plant because
they can be burnt off. Carbon may form as much as one-half
of the dried substance of a plant. The nitrogen seldom exceeds
4 per cent, of the dry matter, and in far the larger number of
cases is present in much smaller quantities, while the amount
of sulphur present is still smaller. The remaining fraction
of the solid part of plants is composed of oxygen and hydrogen,
and a little mineral matter.

The ash of the plant is found, when analysed, to contain
Phosphorus, Potassium, Calcium, Magnesium, and
Iron, along with Silicon, Sodium, Chlorine, and slight
traces of most other chemical elements. Silicon, Sodium, and
Chlorine, are not necessary for the growth of the plant, but are
taken in along with the water.

Chlorine seems to be necessary for the nutrition of Buck-
wheat, Barley, and Oats, for if these plants are grown in
solutions which do not contain this element they do not flourish.

ii8 BOTANY FOR BEGINNERS CHAP.

The elements which are found in the ash of a plant are said to
form the incombustible elements of the plant.

The Essential Chemical Elements of Plant Food.—
The elements which are essential for the life of a green plant
are ten in number. They are as follows : —

Carbon Phosphorus

Hydrogen Potassium

Oxygen Calcium

Nitrogen Magnesium

Sulphur Iron

Water Culture. — The relative importance of the elements
given above to the life of plants can be ascertained by the
method of water culture. The plant is grown in distilled
water in which certain salts have been dissolved. If the solution
contains everything necessary for the growth of the plant, it is
said to be a normal solution. By varying the salts in the
solution in a number of experiments, and observing the effect
produced upon the plants, we can draw certain conclusions as
to the needs of plants.

The following can be taken as an example of a solution for water
culture : —

Distilled water I litre.

Potassium nitrate I gramme.

Sodium chloride \ ,,

Calcium sulphate £ ,,

Magnesium sulphate \ ,,

Calcium phosphate i ,,

A few drops of a dilute solution of iron chloride should be added.

Seeds of any quick growing plant, such as Maize, Bean, Pea, or
Buck-wheat, are germinated on damp saw-dust, and when the
radicles are well-developed, the seedlings are washed in distilled
water. A series of bottles with wide mouths are prepared, and
the corks which fit the bottles are suitably split. The seedling
is then placed in the split made in the corks with its roots
hanging in the solution. A different solution is placed in each
bottle. In one a normal solution is used as a test of the growing
power of the others. If, for instance, the plant is grown in a
solution which contains all the essential elements except iron
the plant is of a pale yellow colour, because iron is necessary
for the development of chlorophyll. If a mere trace of iron is

THE PHYSIOLOGY OF NUTRITION

added to the solution the plant changes its colour and becomes
green. In fact, if some of the leaves are simply washed with a
weak solution of iron they turn green.

When potassium nitrate is left out of the solution the plant is
stunted in its growth.

EXPT. 106. — Weigh a Turnip and place it in a hot oven for a few
days, or until it is perfectly dry. Weigh again, and note the change in
weight. The water in the Turnip has been driven off, and only the
solid matter remains behind.

EXPT. 107.— Twist a piece of stout iron wire many times round two
or three inches of a small branch, and burn the wood over a Bunsen or
spirit flame upon a plate. Note —

(i) The residue of incombustible matter (the ash).

(ii) The bark produces the most ash.

(iii) The colour of the ash is white or grey.

EXPT. 108. — Burn a piece of dry wood in a jar full of air. This can
be done by twisting a piece of wire round the wood to hold it with ;
then light the
wood and hold it
in the jar as long
*as it will smoul-
der. Pour into
the jar a little
lime - water.
Note—

(i) The lime-
water in the bottle
is clear and co-
lourless.

(ii) The lime-
water becomes
milky when
shaken in the jar.

(iii) This being
the test for carbon
dioxide, shows
that when wood is
burnt in air, car-

bon dioxide
formed.

FIG. 143. — Water Culture. — No. i. Pea plant grown in normal
solution. No. 2. Pea plant grown without jxrtassium.
No. 3. Pea plant grown without nitrates or ammonium
salts. No. 4. Pea plant grown with soda instead of
potash. No. 5. Pea plant grown without calcium.

EXPT. 109.—
Germinate a few

Peas in damp sawdust. Obtain five wide-mouthed bottles with corks
and split the corks so that the plants can be suitably fixed. When the
Pea seedlings have their radicles about two inches in length, wash
them in pure water and fix five of the best developed in slits in the

120 BOTANY FOR BEGINNERS CHAP.

corks. Mix five solutions for water culture, and number the bottles
containing them from one to five.

(1) Let the first be the normal solution given on p. 118.

(2) Leave out the potassium nitrate from the second solution.

(3) Mix the third solution without the iron chloride.

(4) From the fourth leave out magnesium sulphate.

(5) In the fifth substitute sodium nitrate for the potassium nitrate.
Measure the plants from time to time. Note —

(i) How the plant grows in the first solution ; the growth will be
normal.

(ii) The plant which is grown without the potassium nitrate is stunted
in growth.

(iii) The plant grown without iron is not green. Wash a leaf with a
weak solution of iron chloride ; it will turn green.

(iv) The plant grown without magnesium sulphate is very stunted in
its growth.

(v) The plant grown without potassium nitrate, but for which sodium
nitrate is substituted, is also abnormal in its growth. This shows that
sodium cannot take the place of potassium.

The Food of Plants. — Plants can only make use of
soluble food, t.e., they can only take in food in solution. The
essential elements can only be assimilated when they are united
to form compounds.

Carbon. — In the experiments in water culture, the solutions
contained no carbon. But if the mature plants at the close of
the experiment be submitted to analysis, half their dry weight
•will be found to be Carbon. Where did the carbon come from ?
Not from the solutions, but from the atmosphere which sur-
rounds the green parts of the plants. The atmosphere may
be regarded as a mixture of gases in the following proportion : —

Nitrogen 79*00 ^

Oxygen 20*96 ]• Parts by Volume.

Carbon dioxide 0*04 J

1 00*00

The green parts of plants are alone able to take in carbon
dioxide and decompose it into carbon and oxygen. That green
plants give out oxygen can be shown by placing a few leaves
of any water plant (Elodea or Water Cress will do) in water,
and exposing them to bright sunlight, when bubbles of gas will
be given off. If these bubbles of gas are collected and exam-
ined, they are found to consist of oxygen. If a green plant, or

THE PHYSIOLOGY OF NUTRITION 121

a portion of a green plant, be placed under a bell jar arranged
over mercury, and containing a measured mixture of air and
carbon dioxide, and be then ex-
posed to light for a few hours, the
volume of the gas under the jar
will remain unaltered.

If after the experiment the gas
is analysed, there will be found to
be less carbon dioxide, but more
oxygen than at the commencement
of the experiment. This shows
that the plant had taken in carbon
dioxide and given out as much FJG I44-_Stem and leaves of

Oxygen as the Carbon dioxide Water Cress giving out oxygen

1 in water. The leaves and stem

taken in. have been cut to allow of the

If a leaf which possesses no escape of the oxygen.

stomata on the upper surface has

a portion of its lower surface coated with wax or vaseline

so that no air can enter through the stomata, no starch can

be found in the covered area, while the adjacent parts of

the leaf become rich in starch. This seems to point to

the conclusion that the carbon dioxide enters through the

stomata.

Recent research shows that : —

1. Under normal conditions, practically the sole pathway for
carbon dioxide into or out of the leaf is by the stomata.

2. Under abnormal conditions, when the stomata or inter-
cellular spaces are blocked, and the pressure of the carbon
dioxide is great enough, it may pass through the cuticle.

Assimilation.— This term is used for all the nutritive
processes which go on in animals, but in botany it is restricted
to the taking in of carbon dioxide by the chloroplasts and sub-
sequent changes which they produce in it. All the other
processes of the plants depend upon the assimilation of carbon
dioxide.

Conditions for Assimilation.— Assimilation by green
plants can only take place under the following conditions : —

i. — A certain intensity of light (either sunlight or electric
light will do).

2. — A certain temperature, at least a few degrees above the

122 BOTANY FOR BEGINNERS ' CHAP.

freezing point. Heat is as necessary here as in all other vital
processes.

If a beam of white light is passed through a prism it is bent out of its
course and split up into a number of colours. These colours are red,
orange, yellow, green, blue, indigo, and violet. This experiment
shows that white light is built up of several primary colours. The
constituents of white light which the chloroplasts use for assimilation
are just the reverse to those used in chemical processes. The rays of
the spectrum, as the decomposed light is called, which act on the
sensitive plate of the photographer, or decompose silver salts, are those
from the violet end ; but the rays which are the most active in assimi-
lation are the red, orange, and yellow. If a plant is grown under
such conditions that only the red, orange, and yellow rays can reach it,
the assimilation is nearly as active as in white light — for 90 per cent, of
starch will be formed against 100 per cent, in white light. On the
other hand, if a plant is grown so that only the violet and blue rays
can pass through, assimilation falls very low, to from 5 to 7 per cent,
only of the 100 in white light.

The changes by which carbon dioxide and water are converted
into organic substances are not fully understood at present. We
only know the final products, not the stages that lead up to them.
The first substance formed in the plant by the constructive
activity of the chloroplasts is some form of sugar. It is most
likely cane sugar. If more sugar is produced than can be
carried away in the sap, it is converted into starch by the
chloroplasts.

If the green parts of any plants are exposed to light,
assimilation commences, and starch appears in the chloroplasts.
If assimilation ceases, as it does regularly at night, the starch
disappears. The disappearance of the starch is due to a
ferment called diastase, which is found in small quantities in
various parts of plants. A ferment is a compound which can
act on another substance, and convert it into a different material.
Ferments may be living or non-living. The Yeast plant is an
example of the former and diastase of the latter.

A very interesting experiment can be performed to show that
assimilation has taken place in a green leaf. From a piece of
tinfoil, cut out the word " Assimilation," and encase a leaf with
it so that the word assimilation is on its upper surface. Allow
the leaf to remain on the tree for a few days, and then bleach
the leaf, and treat it with iodine solution. The word assimila-
tion will appear on the leaf. The whole of the leaf, with the

x THE PHYSIOLOGY OF NUTRITION 123

exception of where it had been exposed to light, is pale in
colour. This shows that light is necessary for the formation of
starch.

Only Green Plants can Assimilate.— Those plants
which are destitute of chlorophyll must obtain their carbonaceous
food in some other form. The Dodder and the Broom-rape
obtain their carbon from the host plant (p. 24) upon which
they live, hence they are said to be parasites. Some plants
obtain the carbon which they require from decomposing
vegetable matter ; they are called saprophytes. The Bird's
Nest Orchid is a good example.

EXPT. no. — Place a little lime water in a saucer, and leave it on a
table for an hour or two.

(i) The surface of the lime water will turn milky.

(ii) This shows that carbon dioxide exists in the air.

EXPT. in. — Prepare some carbon dioxide by acting on marble with
hydrochloric acid. Fit up the apparatus shown in Fig. 145. Place a
few pieces of marble or limestone in
the flask and cover with water ; pour
strong hydrochloric acid down the
funnel till the action is brisk. Col-
lect a bottle of the gas. This can
be done by placing a delivery tube
into the bottle. When the contents
put out a light held just below the
outside of the mouth of the bottle, it
is full of carbon dioxide. Turn the
bottle wrong side up, and place it
over a branch with leaves which is
placed in a glass of water. Expose
to light for a few hours, and then
test with a light. The light will
burn. This shows that the leaf has FlG- MS- -Diagram of apparatus for the

, i- -j i • preparation of carbon dioxide.

taken in carbon dioxide and given

out oxygen.

EXPT. 112. — Place a green plant under an orange or red coloured
bottle. Expose to a bright light for a few days. Examine a leaf of
the plant in the following way : —

(i) Dip the leaf in boiling water.

(ii) Bleach in methylated spirits till white.

(iii) Place in cold water to displace some of the spirits.

(iv) Cover with iodine solution. Note —

(v) The leaf will be coloured blue black. This shows that green
plants use the rays of light from the red end of the spectrum.

If a red bottle cannot be procured, the experiment can be performed
by building around the plant panes of red glass.

124 BOTANY FOR BEGINNERS CHAP.

EXPT. 113. — Place a green plant under a blue bottle, and expose to
light for a few days. Examine a leaf by the same method given in
Expt. 112. Note —

(i) The leaf does not turn so dark in colour with the iodine solution.

(ii) This is due to the blue glass cutting off all the rays except the
blue and violet, and these are not the active agents in assimilation.

Experiments show that the active rays are those from
the red end of the spectrum, but as white light contains
all these rays in addition to blue and violet, there will be even
more starch produced in white light than under the influence of
the red, orange and yellow rays.

EXPT. 114. — Obtain a strip of tinfoil and fix it over a portion of a
leaf, so as to protect it from the light. Leave the leaf on the plant for
a few days. Treat the leaf in the way advised in Expt. 112. Note —

(i) The part of the leaf which has been covered with tinfoil is of a
pale yellow colour.

(ii) The remainder of the leaf is of a dark blue colour.

(iii) This shows 'that light is necessary for the formation of starch.

EXPT. 115. — Take a plant with variegated leaves, and place it in
darkness for a few days. Now place the plant in bright light for two
hours, and treat a leaf as described in Expt. 112. Note —

(i) That it is only the green parts of the leaf which colour blue.

(ii) This shows that it is only the green parts of plants which can
assimilate.

Other Elements in the Food of Plants.— Hydrogen.
All plants can obtain hydrogen from water and ammonium salts.
Hydrogen is necessary for the life of the plant, for it enters into
the composition, as we have seen, of cellulose, starch, proteids,
and protoplasm.

Oxygen. Plants can take up oxygen in a free state, in
combination in water, and in mineral salts.

Respiration. — Free oxygen is necessary for the life of
nearly all living beings. The taking in of free oxygen and the
giving out of carbon dioxide is spoken of as respiration. Every
living cell in a plant requires oxygen for its activity.

// must be distinctly understood that respiration and assimila-
tion are two distinct processes. Green plants are alone able to
assimilate under the influence of light; they take in carbon
dioxide and give out oxygen.

Respiration is carried on by all parts of plants no mattct
what their colour may be, and at all times, from the commence-
ment of germination until the plants die. Oxygen is taken in

THE PHYSIOLOGY OF NUTRITION

125

by living plants and carbon dioxide given out both during
light and darkness.

During assimilation the plant gains weight, but during active
respiration there is a loss of material. The loss is caused by
the oxygen uniting
with the carbon
compounds of the
plant to form carbon
dioxide. This loss
of weight due to
respiration supplies
the plant with
energy, by means
of which it is able
to assimilate. If
a plant which is
growin'g well be
placed in an atmo-
sphere of pure nitro-
gen, or hydrogen, or
in air from which
the oxygen has been
absorbed, the active
life of the plant
ceases at once. It
has been calculated
that one hour's as-
similation will
counterbalance
thirty hours' loss by
respiration.

Heat is Pro-
duced by Respi-
ration. — A ther-
mometer surround-
ed by germinating
seeds registers a

FIG. 146.— Experiment in respiration. B, an inverted
flask containing flowers, which are held in position
by cotton wool, W ; K, solution of caustic potash ;
Q, mercury, which rises in the neck of the flask,
because carbon dioxide is absorbed by the caustic
potash solution. (S.)

rise of temperature.

Flowers which are actively respiring produce both heat and
carbon dioxide. This can be shown by placing a number of

126 BOTANY FOR BEGINNERS CHAP.

flowers in a flask and holding them in position by a plug of
cotton wool pushed into the neck of the flask. Fit the flask in
an inverted position on to a cork through which one end of a
tube (open at both ends) passes. The other end of the tube
dips into mercury on the top of which a strong solution of
caustic potash floats. As the flowers in the flask use up the
oxygen and give out carbon dioxide, since the latter is con-
tinually absorbed by the caustic potash solution, the mercury
rises in the tube. This is because of the diminution of the
pressure inside the flask. If the gas in the flask be tested, a
loss of oxygen becomes evident, and by weighing, the caustic
potash solution can be proved to have increased in weight.
If the temperature of the flask be noted a rise of temperature
will be shown. Fig. 146 shows the apparatus which can be
used for this experiment.

Conditions necessary for Respiration.— The conditions
under which respiration occurs may be stated as follows : —

1. Plants respire in both light and darkness.

2. An atmosphere containing free oxygen is necessary.

3. A certain temperature is most favourable. If seeds are
kept in a cold place they respire slowly, but if moved to a warm
place the respiration increases.

Parts of Plants which Respire vigorously.— The
parts of plants which stand in need of oxygen are : —

1. Every living cell at all times ; dead parts of plants
cannot respire.

2. Germinating seeds which respire with great vigour.

3. All parts which are growing actively. There is always a
rise of temperature due to the very active respiration at these
times.

4. Developing flowers ; during the time of flowering there
is a great demand for oxygen, and a rise of temperature always
takes place.

Use of Oxygen. — Plants require oxygen for two purposes.
In the first place it is necessary for the building up of cellulose,
starch, sugar, proteids, and protoplasm. It is also necessary
for respiration, for without it the plant cannot gain the
necessary energy for the vital processes to be carried out.

EXPT. 116. — Steep a few Peas in water for twenty-four hours, and
place them on damp cotton-wool at the bottom of a bottle. Close the

THE PHYSIOLOGY OF NUTRITION

127

bottle with a tight-fitting cork, and keep the Peas warm for two clays.
Note —

(i) That when the cork is removed and a lighted taper put in, the
flame is extinguished.

(ii) If a little lime-water is shaken in the bottle, it turns milky.

(iii) This shows that some or all of the oxygen has been used up by
the germinating seeds, and that carbon dioxide has been given out.

EXPT. 117. — Place a few Peas on damp cotton- wool at the bottom
of a bottle, and also place in the bottle a test-tube which contains a
solution of caustic potash. Through
the cork pass a glass tube bent into the
shape of a U, as is shown in Fig. 147,
and in the glass tube pour a little
coloured fluid. Note —

(i) The liquid stands at the same
level in both arms of the tube.

(ii) As the experiment goes on, the
liquid rises in the arm of the tube which
is in direct contact with the «air in the
bottle.

(iii) The rise of the liquid is due to
the oxygen in the bottle being used up
by the germinating Peas, and the carbon
dioxide which they give out being ab-
sorbed by the caustic potash. The
pressure in the bottle being less than
the pressvire of the external air the liquid
is forced towards the bottle.

(iv) At the close of the experiment
the caustic potash tube can be weighed,
and it will be found to have increased
in weight.

FIG. 147. — Diagram illustrating
how germinating Peas use up
oxygen and give out carbon
dioxide. A, B, level of co-
loured liquid ; C, D, the
change in level due to oxygen
being used. The carbon di-
oxide is absorbed by the caus-
tic potash in the test-tube.

EXPT. 1 1 8. — Obtain two Potato

tubers of the same weight. Place one to dry in a hot oven, and the
other in a damp dark room. Examine both from time to time, and
note —

(i) The one in the oven, because water is driven off, loses weight.
When it is perfectly dry, weigh it, and record the change in weight.

(ii) The one in the damp dark room commences to grow and pro-
duces small pale leaves and small tubers.

(iii) After a time growth ceases, because the reserve material in the
tuber has been used up.

(iv) Now take the old tuber, with the stems, leaves, and tubers which
have been produced, and place them in a hot oven until all the water
has been driven off.

(v) Weigh the dry residue. It is lighter than the residue obtained
from the first tuber dried in the oven. This loss of weight is due to
respiration. During the whole of the time of growth, oxygen was taken

128

BOTANY FOR BEGINNERS

CHAP.

in and carbon dioxide given out ; but, the plant being in the dark, no
chlorophyll was produced and no assimilation could go on.

(vi) This experiment shows that there is a loss of weight due to
respiration, caused by the oxygen uniting with some of the carbon of
the plant to form carbon dioxide.

EXPT. 119. — Place some germinating Peas in a funnel, as shown in
Fig. 148, so that they surround the bulb of a thermometer. Cover the

apparatus over with a cardboard
box, and pass the thermometer
through a hole in the box. Note —
there will be a rise of temperature,
due to the respiration which goes on.

The Nitrogen of Plants.—
In the water culture experiment
we found that the plant grown
in the solution without com-
pounds of nitrogen was stunted,
and soon died. It died from
want of nitrogen, though sur-
rounding it on every hand there
was plenty of free nitrogen.
Plants cannot use the free nitro-
gen of the air. Nitrogen must
always be presented to a plant
in a combined form. Most

green plants obtain the nitrogen necessary for their growth from
the nitrates in the soil. Nitrates are mineral salts which
contain nitrogen ; they are found in all fertile soils. The nitrates
of the soil may be dissolved by water, which is subsequently
absorbed by the roots and is so introduced into a plant.
Parasites obtain the nitrogen necessary for their growth from
the hosts upon which they live.

Carnivorous Plants are able to obtain the greater portion
of the nitrogen which they require for their growth from the
animals which they are able to entrap.

The Sun-Dew (Fig. 150), which grows on the moors in Lanca-
shire, Yorkshire, North Wales, and many other parts of the
United Kingdom, is a good example of such a plant. The
name Sun-Dew has been given to the plant because, when the
sun shines, it appears to be covered with dew. The leaves are
covered with hairs called tentacles, on the end of which minute

FIG. 148.— Diagram illustrating the rise
of temperature due to respiration.

THE PHYSIOLOGY OF NUTRITION

129

glands are developed. The glands secrete a fluid which is very
much like the gastric juice of the higher animals. It is this

FIG. 149.— Dodder. — In the middle a plant of the Dodder is shown parasitic on a
Willow twig ; b, reduced leaves ; /?/, flowers. On the left a transverse section
shows how the suckers enter the host plant. On the right, the filaments which
are produced from the seeds are shown. (S.)

fluid which causes the plant to appear to be covered with
dew. If a small insect sees the glistening fluid it comes towards

1 3o

BOTANY FOR BEGINNERS

CHAP.

it (doubtless with visions of honey), and a leg or a wing comes
in contact with the end of a gland and the fluid holds it tight.
The struggling insect smears itself more and more with the
deceptive fluid, and, strange to say, all the tentacles on the leaf
begin to move towards the insect. At last it is covered up.
More and more fluid is poured out until all becomes quiet. The
leaf remains closed for a few days, and when it opens a little

FIG. 150.— Sundew.

FIG. 151. — Buttervvort.

indigestible matter is blown away. The remainder has been
absorbed by the leaf for its nutrition.

Another common English carnivorous plant is the Butter-
wort (Fig. 151), which grows in damp places. A rosette of
leaves grows close to the ground. The leaves are of a dirty
yellow colour and are covered with numerous small hairs which
secrete a sticky fluid. The wind! is always blowing the dead
bodies of small animals about, and if one of these comes in con-
tact with the fluid it adheres to it. The margin of the leaf,
which is always somewhat curved, moves a little and pushes
the body before it. The hairs secrete an acid fluid capable of

THE PHYSIOLOGY OF NUTRITION

decomposing the dead bodies, and thus the plant is able to
obtain a portion of the nitrogen which it requires.

In many parts of the ditches, ponds, or pools in Scotland and
Ireland an aquatic carnivorous plant is found. Growing from it
are a large number of small bladders which vary in size from one-
eighth to one-quarter of an inch in diameter. It receives the name
of the Bladderwort (Fig. 152). Each bladder is full of water.

FIG. 152.— Bladderwort.

FIG. 153. — A, bladder of Bladderwort ; B, sec-
tion of bladder ; C, wall of bladder, more
highly magnified.

Entrance into the bladder is effected through the opening at
one end. The opening is guarded by a valve which is a sort, of
a trap-door opening inwards and sloping towards the cavity.
The valve is guarded internally by a number of stiff hairs,
and the external opening is protected from large animals by
long multicellular hairs. The bladder (Fig. 153) is lined
with a number of cells which can absorb materials from the
bladder.

The whole of the apparatus is a trap for small aquatic animals.
They can enter but never return. The animal pushes against

K 2

132

BOTANY FOR BEGINNERS

CHAP.

the door, which gives way and allows it to enter. It tries again
and again to push the door open but it will only open inwards.
After a time it dies ; decomposition sets in, and the products are
absorbed by the cells which line the bladder.

In most parts of the world there are carnivorous plants.
Well-known examples are the Venus's Fly-trap (Fig. 154), which

grows in South America,
and the Pitcher plants,
which are very widely dis-
tributed.

Most of these plants
grow in soil which is
very poor in nitrates, with
lowly bog plants for their
companions. It is only
through their power of
entrapping small animals
that they are able to live.
It has been proved by
experiments that if car-
nivorous plants are grown
so that no animal food
can be obtained that they
are stunted in their
growth.

Leguminous Plants
—The members of the
Bean family can obtain
the nitrogen which they
require in a different way

from most plants. If a Clover or Pea-plant is pulled up and the
roots examined, they will be seen to be covered with a number
of nodules, or root-tubercles, as they are called. These are
produced by Bacteria," which are themselves minute plants. The
Bacteria penetrate through the root-hairs into the cortex of the
root, and so produce the tubercles. The Bacteria live in and
around the tubercles in the soil, and take free nitrogen from
the air in the soil, and build up this nitrogen into compounds,
which are passed on to the plant. The plant most likely gives
carbonaceous compounds to the Bacteria in return for nitrogen.

FIG. 154.— Venus's Fly-trap.

THE PHYSIOLOGY OF NUTRITION

133

The Bacteria form with the Leguminous plant a life partnership,
which is called Symbiosis. That it is an advantage for the
Leguminous plants to have the Bacteria living in the soil is
certain, for those plants with the best
developed tubercles thrive the best.

The relation of the Bacteria with
the plants which belong to the Bean
family is so well known that farmers
can now obtain Bacteria to mix with
the seeds of the above plants when
sowing. This material which is
mixed with the seeds receives the
name of nitragm. If a little soil
from a field "where plenty of root-
tubercles are produced be taken and
applied to a soil which will not pro-
duce root-tubercles, these will then
be produced, and the plant will be-
come strong and healthy.

EXIT. 1 20. — Pull up a well-developed
Clover plant and examine the roots.
Note —

(i) The tubercles on the roots. These
are shown in Fig. 155.

(ii) Cut a transverse section of a root
so as to pass through a root tubercle and
examine it with a hand-lens.

(iii) Mount a transverse section of a
root having a root-tubercle in water.

(iv) Examine under a high power, and
note the structure.

EXPT. I2i.— Pull up a stunted Clover
plant and examine the roots. Note —

(i) The roots have either only very few
tubercles or they are entirely absent. FIG. 155.— Root-tubercles on the

(ii) The general appearance of the roots of a Leguminous plant,
plant.

(iii) Experiments 120 and 122 show

that the tubercles exert a favourable influence on the growth of the
Clover.

EXPT. 122. — Prepare two plant pots in the following way — (a) Fill
one with rich soil from a field in which Clover grows to perfection ;
(b) fill the other one with sand which has been raised to a high

134 BOTANY FOR BEGINNERS CHAP.

temperature by placing in an old tin and applying heat to it. Sow a few
Clover seeds in each ; give to (a) water only, but to (b) give the solution
described on page 118. From time to time pull up a plant from each
pot and examine. Note —

(i) The difference in the size of the plants.

(ii) The difference in the root-tubercles.

Remaining Elements in Plants.— Sulphur.— Plants
take in sulphur in the form of sulphates. The sulphates of
ammonia, potassium, and calcium are the most useful to the
plant. Sulphur enters into the composition of proteids and
protoplasm, and without it these materials cannot be formed.

Phosphorus. — Plants take in phosphorus as phosphates. A
common phosphate is calcic phosphate, or phosphate of lime.
Phosphorus enters into the composition of the nucleus, and
appears to aid those chemical changes upon which the life of
the plant depends.

Potassium. — There is a very large variety of forms in which
potassium can be absorbed by plants, such as sulphates,
phosphates, and chlorides. As a rule clay soils possess plenty
of potassium, and it is very seldom that a compound of potassium
is applied as a manure. This element is very active in assimila-
tion and in the formation of protoplasm. The solid matter of a
plant contains as much as 3*5 per cent, of potassium.

Calcium. — The calcium which a plant requires for its growth
is absorbed in the form of sulphates, phosphates, or nitrates.
The work which calcium plays in the economy of the plant is
not fully understood. Plants cannot live without it, and
the effects of an insufficient supply is shown by their retarded
growth.

Magnesium. — Magnesium can be taken in by plants from all
its compounds except the chloride, which seems to be injurious.
Very little is known as to the use of magnesium, but our experi-
ments in water culture show that it is necessary for the healthy
growth of the plant.

Iron. — Green plants, as we have seen, require iron in their
food for the formation of chlorophyll. This element can be
absorbed from a variety of compounds, and it is only an
essential element for the nutrition of green plants.

The Non- Essential Elements of Plant Food.—
A very large number of elements which plants take in with
their food they can do without.

THE PHYSIOLOGY OF NUTRITION 135

Silicon. — This element is taken in by the roots of plants in the form
of soluble silicates. It is very largely deposited in cell-walls, and
probably protects the plant from the attacks of fungi which are unable
to penetrate through external walls in which silicon is present. Wheat
and all the cereal grains have a very large quantity of silicon in their ash ;
the ash of wheat-straw contains as much as seventy per cent, of silicon.

Sodium. — Sodium is one of the most widely distributed of all the
elements, and it is no wonder that it is contained in the ash of all plants.

Chlorine. — The ash of all plants contains a little chlorine, but it is
not essential for their nutrition. Buck-wheat, Barley and Oats seem
to grow better if they are supplied with chlorine ; Maize will grow in
solutions without it. Chlorine and sodium, in the form of common
salt, seem to keep plants healthy.

SUMMARY.

Physiology. — The division of botany which deals with what a plant
can do is termed physiology. All the higher plants show division of
labour, i.e., each part of the plant performs a special kind of work.

Nutrition.- — The processes which enable a plant to obtain and
change its food, thus enabling the plant to form new tissue, is spoken
of as nutrition.

The Essential Elements of Plant Food are—

I. Carbon 2. Hydrogen 3. Oxygen 4, Nitrogen

5. Sulphur 6. Phosphorus 7. Potassium 8. Calcium

9. Magnesium 10. Iron

Water Culture. — When a plant is grown in a solution the ingredients
of which are known, we can find out what the plant requires for its
growth. This method is termed water culture.

The Food of Plants.— Plants can only take in their food in the form
of compounds and in solution.

Carbon is obtained by green plants from the carbon dioxide of the
atmosphere. Only the green parts of plants can decompose carbon
dioxide. Carbon dioxide passes into the plant through the stomata.

Assimilation. — The absorption of carbon dioxide and its conversion
into organic compounds is called assimilation. The conditions neces-
sary for assimilation to take place are — (l) A certain intensity of light ;
(2) A certain temperature. The red parts of white light are the most
active in assimilation.

Parasites and Saprophytes. — Plants destitute of chlorophyll take in
'their carbon in the form of carbon compounds other than carbon dioxide.
Those plants which live on decomposing matter are called saprophytes.

The Hydrogen necessary for a plant is obtained from water and
ammonium salts.

Oxygen is required by a plant (a) in a combined form as a food, and
''(b) in a free state for respiration.

Respiration. — All plants must have free oxygen for respiration.
This oxygen unites with the carbon of the plant and forms carbon
•dioxide, which is given out by the stomata. Respiration and assimil-
ation are two different processes ; the plant gains by the first the energy
necessary for assimilation and growth, by the latter it gains weight.

136 BOTANY FOR BEGINNERS CHAP, x

Heat is produced by respiration. Plants respire (i) In both light
and darkness ; (2) In an atmosphere containing free oxygen ; (3) At a
certain temperature— a few degrees above the freezing point.

The parts of plants which respire are — (i) Every living cell, (2) Ger-
minating seeds, (3) The growing parts of plants, (4) The flowers.

Nitrogen. — Most green plants obtain the nitrogen necessary for their
growth from the nitrates in the soil.

Leguminous Plants obtain most of the nitrogen for their growth
through the agency of Bacteria, which grow in tubercles on their roots.
They are said to live in Symbiosis with the Bacteria, i.e., there is a life-
partnership between them.

QUESTIONS ON CHAPTER X.

1 i ) What is meant by plant physiology ?

(2) Explain what you understand by "division of labour"?

(3) What do you know about —

(a) The amount of water found in plants ?

(b) The solid matter of a plant ?

(4) Enumerate the essential chemical elements which a green plant
absorbs as food from the soil ? and briefly state what is the special use
of each element. (1891.)

(5) Explain why it is that starch-grains are formed in the chlorophyll
corpuscles when a leaf is exposed to light and air.

(6) Explain how it is that a green plant cannot carry on its nutrition
in darkness (1892).

(7) What part of its food does a green plant obtain from the air ? In
what form, and under what conditions, is it taken in ? (1889.)

(8) What are the conditions necessary for the assimilation of carbon
by green leaves ? State the means by which you would prove that a
given leaf had been assimilating carbon. (1891 T.)

(9) Give an account of the use of chlorophyll in the nutritive pro-
cesses of plants. ( 1 890 T. )

(10) From what source and in what forms do plants usually absorb
their nitrogenous food ? Mention cases in which the nitrogenous food
is absorbed from other sources and in other forms. (1887.)

(12) Plants both absorb and give out carbon dioxide. State pre-
cisely the circumstances upon which each process depends. (1885.)

(13) In what respects does the nutrition of the leguminous differ from
that of the other green plants ? Explain the significance of this differ-
ence. (1896.)

(14) What is starch? Explain how it is that, if a green plant be
kept for a day or two in darkness, no starch is to be found in its leaves.
(1897.)

(15) How may the necessary chemical elements for the nutrition of
a green plant be determined ?

(16) What is the importance of carbon to a plant? From what
source does a green plant get its carbon, and how is it assimilated ?
(1899.)

CHAPTER XI

THE ABSORPTION AND MOVEMENT OF WATER IN THE
PLANT

Absorption of Water and Minerals.— It is a well-
known fact that if plants are not supplied with water they cease
to grow ; they droop, wither, and die. All the
substances which a plant requires for its growth
are taken from the soil with the exception of
carbon^ and this, as we have seen, is obtained
from the air. That the roots are the organs
which take in water is shown by the experiments
in water culture. The parts of the roots active
in absorption are the rqpt-hairs, and the
uncuticularised portions of the younger
roots. Root-hairs are unicellular and thin-
walled, the walls being lined with protoplasm.
These root-hairs pass between the particles of
the soil, and by their intimate connection there-
with absorb water which contains minerals in
solution. Even in a dry soil there is a certain
amount of water round the particles, held there
by capillary attraction. This water may pass
from particle to particle by the same capillary
force. Capillary attraction similarly causes
water or tea to completely saturate a piece of sugar if one corner
is wetted ; it also determines the flow of oil up the wick of a lamp.

EXPT. 123. — Obtain two slips or pieces of window glass and a tumbler
partly filled with a coloured liquid. Place the pieces of glass so that

FIG. 156. — Tip of
root-hair, with
adhering parti-
cles of soil.

(X240.) (S.)

I38 BOTANY FOR BEGINNERS CHAP.

there is a little space between them, and dip them into the liquid in the
tumbler. Note —

(i) The coloured liquid rises between the slips of glass.

(ii) The height to which it rises will depend upon the width of the
opening between the slips. The greater the distance between the slips
of glass the shorter the column of liquid ; and the nearer they are together
the higher the coloured water will rise.

(iii) The liquid rises by capillary attraction.

The finer the particles in the soil the more water will be held
by it. The interspaces between the particles of the soil form so
many capillary tubes, up which the water rises, and by which it
is held.

Absorption.— The root-hairs make their way into the
interspaces, and come into close contact with the water round
the particles. The water gradually diffuses through the thin
cell-wall of the root-hair, or uncuticularised portion of the root ;
it thus reaches the interior of the root-hair and eventually passes
up into the plant, while a little acid sap diffuses out from the
cell into the soil. That plants do take in water by their roots
can be shown by growing a plant in water in which a little eosin
has been dissolved. The solution of eosin is taken in.
the roots being stained internally for a considerable distance
above the water. Only those substances in the soil which are
soluble in water can be taken in by the plant. This can be
shown by the following experiments.

EXPT. 124. — Put a little powdered eosin in water, and place the roots
of an actively growing plant so that they dip into the solution. Leave
the roots of the plant in the solution for several hours, and examine in
the following way : —

(i) Examine the root ; it will be coloured externally for a short
distance above where the water stood.

(ii) Cut a transverse section of the root and mount it in glycerine.
Examine under the low power of the microscope ; the section is seen to
be stained right through.

(iii) This shows that the soluble eosin can pass along with the water
through the cell-walls.

EXPT. 125. — Place a little powdered carmine in water, and place the
roots of an actively growing plant so that they dip into the mixture.
Note—

(i) The carmine does not dissolve, but remains suspended in the water,

(ii) Cut a transverse section of the root and mount in glycerine.
Examine with the low power of the microscope. Observe the carmine
has not passed into the plant, for the section is not coloured.

(iii) It is only the soluble constituents which can pass through the
cell-wall along with the water.

xi ABSORPTION AND MOVEMENT OF WATER 139

Osmosis. — Since nutrient substances must pass through the
closed walls of cells in order to reach their interior, it follows
that they must be in a soluble condition.

How is the interchange between the fluid in the plant and
that in the soil brought about ? The cell-sap in the plant is
separated from the water in the soil by the permeable cell-walls.

The absorption of the solution from the soil is nothing more
than a mixing of two fluids of different densities. The mixing
of fluids through a permeable membrane is called osmosis, and
for this to take place it is necessary for the fluids to be of
different densities. There are two currents set up, one from the
exterior of the plant to the interior called the endosmotic
current, and one from the interior of the plant to the exterior,
called the exosmotic current. Since the cell-sap is much
richer in substances which set up osmotic currents than the
water in the soil, or in other words is heavier bulk for bulk, a
considerable endosmotic current of \\-ater from the soil is set up
while very little of the cell-sap passes into the soil. The giving
out of the acid cell-sap by the plant in exchange for the solution
in the soil plays a very important part in absorption. In the soil
is a variety of materials insoluble in pure water but which are
dissolved in a weak acid. If a plant is grown over a slab of
polished marble so that the roots come in contact with it, the
acid sap in the cells of the younger portions of the roots leave
their impression on the slab of marble. These impressions
are produced by the acid cell-sap dissolving some of the
marble.

EXPT. 126. — (i) Dip a piece of bhie litmus paper in a weak solution
of sulphuric acid. Note —

(ii) It turns red.

(iii) Dip a piece of red litmus paper in a little caustic soda solution ; it
changes its colour and becomes blue.

(iv) These tests are used to see if a substance is acid or alkaline.

EXPT. 127. — Pull up a grass plant b/ the roots and place a piece of
blue litmus paper against the tip of a young root. Note—
(i) The paper gradually becomes red.
(ii) The roots are therefore acid.

EXPT. 128. — Obtain a piece of limestone or marble and polish it by
rubbing one side on a piece of flagstone. Place the polished limestone
in a pot along with some soil, and plant a young seedling above the
limestone. Keep the plant moist and place the pot where there is

140 BOTANY FOR BEGINNERS CHAP.

plenty of light. At the end of some twelve weeks pull up the plant,
take the piece of limestone out, and wash it. Note —

(i) The markings on the limestone show where the roots have
touched.

(ii) These markings have been produced by the acid sap which the
roots gave out.

(iii) In the soil under ordinary conditions the acid sap performs the
same kind of work.

Conditions Necessary for Absorption.—

i. — The air which surrounds the plant must have a certain
temperature. There is a minimum temperature below which no
absorption will take place, and a maximum above which this
process will cease. Between these two extremes a temperature
can be found for each plant at which the process is most
vigorous, and this temperature is said to be the Optimum
temperature,

2. — The soil (or culture splution) must also have a certain
temperature before absorption can take place. The roots of a
plant take in very little water in winter because the soil is very
cold ; in summer a larger quantity is taken in because the soil
is warmer.

3. — The strength of a culture solution has a very decided
effect on absorption. If the solution is very strong the plant
cannot take it in ; absorption only goes on when the solution
is very weak — the condition found in the soil in ordinary
circumstances.

Plants give out Moisture. — Plants not only take in water
but they also give it out. This is shown by the atmosphere of
forests always being moister than places without vegetation. It
has been calculated that a good-sized Oak tree will give out
in a single day several gallons of water, and during the active
life of a Sunflower plant, it will give out 200 times its dry
weight of water. That plants lose water is shown by cutting a
branch, weighing it, and placing it in a dry place. A second
weighing in the course of a few hours will show it to have lost
weight.

Transpiration. — The way in which the plant gives out the
moisture must now be considered. This giving out of moisture
by a plant in the form of vapour is called transpiration. It
is only those parts of plants which are in contact with the air

xi ABSORPTION AND MOVEMENT OF WATER 141

which can transpire. The following experiments will show that
plants lose water : —

EXPT. 129. — Take up three well -developed Mustard plants by their
roots and put one in a dry place, such as on a table in a warm room.
Place another with its roots in water, and the third in a dark cupboard.
Examine at the end of a few hours. Note —

(i) The plant placed on the table is withered.

(ii) The one in the dark cupboard is in a far better state than
the first.

(iii) The plant in water is unaltered ; the roots have taken water in as
fast as it has been transpired.

(iv) Plants give out water more actively in a light than in a dark
place.

EXPT. 130. — Obtain a potted plant, and cover the soil either with
tinfoil or cardboard to prevent evaporation from it. Now place the
pot and its contents on the pan of a scale and weigh it. Note —
(i) That the pot and its contents lose weight.

(ii) This must be due to the leaves and stem giving out moisture.

(iii) The longer it stays on the scale the lighter it becomes.

(iv) This experiment can be performed before a class even in winter,
using either the electric light or gas.

EXPT. 131. — Cover the soil of a potted plant with tinfoil or card-
board as before, and cover the plant with a bell jar, and place the whole
arrangement in sunlight. Note —

(i) The inside of the jar is soon covered with moisture.

(ii) The moisture disappears at night.

(iii) There is only one source for the moisture, viz., the leaves and
stems of the plant.

(iv) The moisture disappears at night because the plant no longer
transpires ; the moisture is condensed and runs down the jar.

To Prove that a given Green-leaf is losing
Moisture. —

EXPT. 132. — Place some white blotting paper in a weak solution of
cobalt chloride. Dry^the paper either by holding it before a fire or in
direct sunlight ; it turns blue.

Hold a piece of this paper near a leaf which is still on the tree.
Note —

(i) That the paper slowly becomes red ; the quicker the colour changes,
the more moisture the leaf is giving out.

(ii) A similar piece of paper should be exposed to the air at the same
time as a test of the atmospheric condition with regard to moisture.

EXPT. 133. — There is, as a rule, more moisture given off by the under
side of a leaf than by the upper. This can be proved by fixing the leaf
of the Oak or Beech with a piece of cobalt paper on each face and
enclosing it between slips of glass. Note —

The one fixed to the loA\;er side assumes the red colour far more
quickly than the one on the upper side.

142

BOTANY FOR BEGINNERS

CHAP.

The Organs of Transpiration.— The epidermal tissue of
a plant is generally more or less cuticularised (p. 76), and the
amount of water vapour which can be given out by the epi-
dermis depends upon the degree of cuticularisation. In plants
where the epidermis is covered by a well-developed cuticle,
very little water vapour is given out. If the cuticle is very thin
or absent, as in the case of water plants, the leaves droop
and wither far more quickly than those with a well-developed
cuticle. Those parts of plants which are covered with cork, or
with wax, possess a protection against a too rapid loss of
water. The Potato is covered with a thin layer of cork, which
prevents loss of water through evaporation.

The principal organs by which water vapour is transpired by
plants are the Stomata and the Lenticels. The stomata are
very small, in fact so small that neither dust nor water can pass
through them into the plant ; but their enormous numbers more
than makes up for their small size. It is calculated that a Sun-
flower leaf contains some thirteen million stomata, and that an
ordinary leaf of a cabbage may contain eleven million.

Changes in Size of the Stomata.— The stomata also regu-
late, transpiration by changes in their size. They open in bright
light, and close in darkness or in foggy
weather. The opening and closing de-
pends upon the amount of light which they
receive. The guard cells (p. 94) contain
chlorophyll, and when light shines upon
them the chloroplasts commence to as-
similate and form sugar. In this process
water is used up, and the cell-sap becomes
denser ; a current of sap is thus set up
from the cells in contact with them to the
guard cells. As more and more sap is
of absorbed by the guard cells, they become
Stoma. s, guard cell, tense, or turgid, and being fixed, they
s"h guard1 cell^wlth shorten and become curved. The small
curved lateral wall. (S.) opening which appears between them is

called the stoma.

The stomata close in darkness because then the chloroplasts
can no longer assimilate. The sugar which has been previously
produced is removed by the movements of the sap, and the sap

FIG i — D'a am
'

xi ABSORPTION AND MOVEMENT OF WATER 143

in the guard cells returns to its normal strength. Figures 157
and 158 show the opening and closing of the stomata.

Lenticels and Transpiration.— The lenticels (p. 108)
which are formed in the periderm of a woody plant also give
out water vapour ; but the quantity so lost can only be small.
The lenticels communicate with the intercellular spaces in the
plant, much in the same way as stomata communicate with the
intercellular spaces in the leaf. In winter the lenticels are
closed by ordinary periderm, but they are open in summer.

Force exerted by Transpiring Shoots.— If a branch is
cut from a tree, and the cut end is placed in water, it will re-

FIG. 158. — Stoma in transverse section. The darker lines show the shape of the
stoma when open, and the lighter lines when closed. (S.)

main fresh. This shows that the branch can take in water by
its cut end. The force which such a branch can exert while
actively transpiring can be measured by the following ex-
periment.

EXPT. 134. — Cut a branch from an Oak tree when the leaves are
fully developed, and fix it in an air-tight manner in a glass tube filled
with water, the lower end of which dips into a cup of mercury. Note —

(i} The volume of the water decreases.

(?.i) The mercury rises in the tube.

(iii) This is caused by the suction exerted by the transpiring shoot.

(iv) The water in the tube disappears to make good that lost by
transpiration.

(v) Thus the mercury is forced up the tube by atmospheric pressure.

Conditions Necessary for Transpiration.—
i. A certain intensity of light ; the stronger the light the
greater the transpiration.

144

BOTANY FOR BEGINNERS

CHAP.

(2) The drier the air the more rapid the transpiration ; this
is shown by noting how soon a plant withers on a very dry day,
and the fresh appearance of a plant on a damp, foggy day.

(3) A windy day is favourable to transpiration. If a plant is
placed where there is a draught it fades more quickly than if
placed where the air is still.

Why Plants Transpire.— The effects of transpiration on
the economy of plants are very important and far-reaching.
These effects may be summarised as follows : —

(1) Transpiration is the principal way in which plants get rid
of the excess of water taken in by the roots. The solution
absorbed by the roots from the soil only contains a small
quantity of dissolved salts ; but since very large quantities of the
weak solution are absorbed, the parts of the plant where growth
is going on still obtain sufficient mineral matter.

(2) Transpiration plays a very important part in the distribu-
tion of salts throughout the plant. The water vapour which is
given out through the stomata and lenticels causes a current
of sap to be set up from the roots to the leaves, and other parts

of the plant. The salts are distri-
buted by the ascending current
to all parts of the plant where
they are required.

(3) Transpiration aids the ab-
sorption of water and salts by
the roots. If a plant is growing
in a water culture solution, and
is covered by a bell-jar, the
transpiration is continuously
reduced, until at last it stops
altogether. If the bell-jar is
removed, transpiration increases
again, because the water vapour
can now escape.

Liquid Water Given out
by Plants. — If the leaves of
Grasses, Buttercup, Strawberry, Lady's Mantle, and most other
plants be examined on a summer morning, drops of glistening
water will be seen to hang from them. For a long time it was
thought that these drops had been deposited on the leaves from

FIG. 159.— Leaf of Nas-
turtium giving out
clops of water. (S.)

xi ABSORPTION AND MOVEMENT OF WATER 145

the atmosphere. They were said to be drops of dew. But in
far the larger number of cases the water has been pumped out
of the water-pores. The roots have taken in an excess of water,
which has been forced up the stem to the leaves. In these
plants transpiration is reduced to a minimum, and the water
exudes from the water pores, stomata, or through the epidermis.
These drops are evaporated as the sun gains more and more
power. A deposit of carbonate of lime, or some other mineral
which encrusts the leaves, is often left behind, as in the London
Pride, Gooseberry, and Currant.

EXPT. 135. — Examine a leaf of the Lady's Mantle on a warm summer
morning. Note —

(i) The leaf forms a little cup, and is shaped like a mantle with a
number of lobes.

(ii) The cup of the leaf is often filled with water which has oozed out
of every leaf-tooth.

(iii) That after emptying the leaf, drops of water ooze out of the end
of the leaf-teeth and collect in the bottom of the leaf.

EXPT. 136. — Examine the leaves of the Arum, also known as the
Cuckoo-pint, or Lords and Ladies.

(i) The leaves are very long (from 6 to 10 inches), and are hastate-
cordate in shape.

(ii) Drops of water can be seen to fall from the tips of the larger
leaves at very short intervals.

EXPT. 137. — Place a bell-jar over some grass plants which are grow-
ing actively. Note —

(i) The leaves, which were dry to commence with, become in a short
time covered with drops of moisture.

(ii) Remove the bell-jar, and the moisture evaporates into the
atmosphere.

Root-Pressure. — If the stem of a vigorously-growing plant,
such as the Indian Corn or Sunflower, be cut off just above the
soil, and the cut surface be dried and examined by a hand lens,
water is seen to ooze out of the cut vascular bundles. It is also
a well-known fact, that if a vine is cut in spring, the cut stem
will bleed ; but if it is cut in summer, when the foliage leaves are
fully developed and transpiring, it will not bleed. The power
which the roots possess of forcing water up the stem is called
root-pressure.

The amount of this pressure can be measured by cutting off
the Gtem of a plant just above the surface of the ground, and

146

BOTANY FOR BEGINNERS

CHAP.

fixing on the cut end a manometer (Fig. 160). The pressure is
often sufficient to force the mercury up the tube to a height of

several inches. In the Nettle
the root-pressure observed has
been found to be sufficient to sup-
port a column of mercury about
1 5 inches high.

How Root-Pressure is Set
Up. — In spring the root-hairs are
very active, taking in large quanti-
ties of water from the soil, which
passes by osmosis into the cells of
the cortex, and when these become
filled with water it is forced into
the vessels of the xylem. The force
with which the water is pumped
from the parenchyma cells of the
cortex into the vessels of the xylem
is produced by the activity of the
root-hairs in absorbing more water
than can be stored up in the cells
of the root.

Thus the phenomenon of root-
pressure depends upon the tempera-
ture of the soil (p. 140), for it is
only when absorption is active that
it can take place.

FIG. 160. — Apparatus for measuring
root-pressure. The glass tube
g is joined to the cut stem j by
means of the rubber tubing c.
The mercury Q is forced up the
tube by the water IV, which is
given out by the cut stem. (S.)

Ex FT. 138. — Cut off the stem of a
Dahlia or Sunflower just above the soil,
and fix to the cut end a hollow glass
tube which contains a little coloured
water. The fixing can be done by
sliding the glass tube over the end of

the stump and using rubber bands to hold it in place, and to pack
the base of the tube. Note—

The water is pushed higher and higher up the tube against the pres-
sure of the atmosphere. The weight of the water lifted will give the
amount of the root pressure.

EXPT. 139. — Jn spring, cut off a branch of the Barberry,
(i) A whitish fluid, the sap, oozes out of the cut end.
(iij The sap is forced out by the root-pressure.

Note—

ABSORPTION AND MOVEMENT OF WATER

How the Water Travels from the Roots to the
Leaves. — The water which, as we have seen, is forced into
the xylem vessels of the root finds its way to the leaves (as far as
we know at present) up the interior of the vessels of the
stem. Professor Dixon, and Dr. Joly, found that if they
blocked up the interior of the vessels with paraffin-wax, only a
little water found its way up the stem, and the leaves on the
branch soon flagged. It would take far too long for the large
quantity of water which the plant requires to pass either up the
parenchyma cells, or through the cell walls. The water is able
to move faster up the interior of the vessels than in any other
direction.

The Transpiration Current.— The current of water
which passes up the stem from the roots to the leaves, to make
good that lost by transpiration, is called the transpiration

FIG. 161. — Diagram illustrating how the water moves up a stem, i, A normal
branch from the Oak in water, the leaves of which are fresh ; 2, a branch of the
Oak with the tissues removed down to the new wood ; 3, a similar branch with
the new wood taken out, the leaves are dried up ; 4, 5, sections of the same.

current. This current travels up the stem of a woody plant,
but only through the outer and younger rings (p. 107). The
heart wood of an old tree never takes part in the conduction of
water, but only the newer rings of the sap wood. The reason
why the transpiration current ascends as it does in some trees
to a height of over a hundred feet is not fully understood, and

L 2

148 BOTANY FOR BEGINNERS CHAP.

is one of the problems of plant physiology which requires
solving.

The following experiments will demonstrate how the sap
travels in woody plants.

EXPT. 140. — Obtain a woody plant, such as an Oak, which is grow-
ing in a pot. (a) From one branch remove a ring of tissue down as
far as the new wood, i.e., cut away the bark cortex and phloem, and
pack the wound with cotton wool to prevent the entrance of fungi.
(b) From another branch remove a ring of the new wood, and replace
the bark and cortex. Note —

(i) The leaves on the branch, which has only a ring of tissue removed,
down to the new wood, are still green and fresh.

(ii) The leaves on the branch, which has had the new wood removed,
have flagged ; they ultimately die.

(iii) The water, which makes good that lost by transpiration, travels
in the new wood, but neither in the cortex nor in the bark.

EXPT. 141. — In many parts of the country old trees may be seen
which have lost their heart wood, as well as the outer tissues of the
plant. When such a tree is encountered, the following observations
should be made. Note —

(i) That leaves are still produced on the upper part of the old stem.

(ii) That the leaves are green and fresh.

(iii) These leaves must be supplied with water. This can only take
place through the new wood, because the heart wood and the outer
part of the tree have decayed. The water travels only through the new
wood.

How the Elaborated Sap Travels in Plants.— The
sap which is acted on in the leaves by the chlorophyll and proto-
plasm, and which becomes very rich in organic compounds, is
called elaborated sap. This is distributed to those parts of
the plant where growth is going on, or where reserve material
is stored up. How is this elaborated sap distributed ? If a
leaf is examined the xylem will be found distributed over the
upper surface of the leaf, and the phloem on the under side.
The xylem brings water and minerals in solution to the cells of
the leaf ; when this has undergone the necessary changes, and is
fit for the nourishment of the plant, it is carried away down the
phloem. Different materials are produced in the leaf by the
activity of the chloroplasts and protoplasm. These materials
can be divided into proteids, fats, and carbohydrates (p. 85-7).
Each of these is distributed in a different way throughout the
plant. The proteid substances in the elaborated sap travel

xi ABSORPTION AND MOVEMENT OF WATER 149

along the sieve tubes of the phloem, and from cell to cell by
osmosis, to those parts of the plant where they are needed.

The carbohydrates (sugars) travel in solution along the
parenchyma cells which surround the vascular bundles in the
leaf and belong to the cortex of the stem.

The needs of the various parts of the plant cause the current
to move to those places where material is being used up in
the formation of new cells, or is being stored up as reserve
material.

EXPT. 142. — From the plant used for Experiment 140, cut away
from a branch a ring of tissue so as to remove the phloem. Note —
The branch below the cut will not increase in size unless elaborated sap
is brought from some other part of the plant, and, as a rule, this does
not take place.

EXPT. 143. — Remove a branch from a woody plant, such as the
Beech, and at about nine inches from the base remove a ring of
tissue down to the new wood. Place the branch in water. Remove
another branch, and place it in water without injurying it. Note —

(i) New roots are produced from the portion of the stem above the
place where the ring of tissue has been removed.

(ii) No adventitious roots are produced from the portion below the
wound, because no elaborated sap can pass through the wound because
it can only travel through the phloem, and this has been removed.

(iii) The branch from the tree which was placed -in water without
being injured produces roots from the tip of the stem.

SUMMARY.

Absorption of Water and Minerals. — All materials (with the exception
of carbon} which plants require for their growth are taken in by the
root-hairs and uncuticularised portions of the root.

Absorption. — That roots absorb is shown by placing the roots of a
plant in a solution of eosin, when their internal parts are stained.

Osmosis. — The mixing of fluids through a permeable membrane is
called osmosis ; for osmosis to take place it is necessary for the fluids to
have different densities.

The sap given out by roots can dissolve some of the insoluble con-
stituents of the soil.

Conditions necessary for Absorption. —

(1) The air surrounding the plant must have a certain temperature.

(2) The soil or solution in which the plant is growing must also have
a certain temperature.

(3) The strength of the solution has a decided effect on absorption.
Plants give out Moisture. — Places with a prolific vegetation have a

moist atmosphere. An Oak tree gives out many gallons of water on

150 BOTANY FOR BEGINNERS CHAP.

bright summer days ; a Sunflower during its active life gives out 200
times its dry weight of water.

Transpiration is the giving out of water vapour by a plant. Only
those parts of a plant in contact with the atmosphere can transpire.

The Organs of Transpiration. — Stomata and lenticels are the organs
by which plants lose the greater portion of the water vapour which
they give out.

Conditions favourable to Transpiration.— (i) A certain intensity of
light; (2) a dry atmosphere ; (3) a windy day.

Why Plants Transpire. — (i) To get rid of the excess of water taken
in by the roots ; (2) to aid the distribution of salts throughout the
plant ; (3) to aid absorption of water and salts by the roots.

Liquid Water given out by Plants.— Plants like the Lady's Mantle,
Buttercup, and Arum give out liquid water through water pores,
stomata, or epidermis.

Boot Pressure is the power which roots possess of forcing water up
the stem.

How Boot Pressure is Set Up. — Root-hairs are very active in spring,
and take in large quantities of water until all the cells of the roots are
filled. The water from the cells exudes into the vessels of the xylem,
and it is then forced up the stem to the leaves.

Water Travels in Plants up the interior of the vessels of the new
wood.

The Transpiration Current is the current of water which passes up
the stem to make good that lost by transpiration. It either passes up
the younger and oute£ rings of the wood (woody plants), or through
separate vascular bundles (herbaceous plants).

Elaborated Sap has been acted on by the chlorophyll and protoplasm
in the leaves. It travels in the following ways — ( i ) The proteid sub-
stances in it pass along the sieve tubes ; (2) the sugars move through
the parenchyma cells round the vascular bundles ; (3) a slow movement
occurs from cell to cell to make good the loss due to growth.

QUESTIONS ON CHAPTER XI.

(1) What part of its food does a green plant obtain by means of
roots? How does the root absorb food ? (1897.)

(2) What do you know about —

(a) The materials found in a fertile soil ?

(b) The substances found between the particles of a soil?

(3) Define the term osmosis. Explain the part which osmosis plays
in the nutrition of a plant.

(4) What conditions are necessary for absorption?

(5) What are the functions of the root? Briefly explain the relation
between the structure and functions of a root. (1893.)

(6) Explain why it is that plants droop on a hot day and recover their
freshness in the evening. (1889.)

(7) What is the "transpiration current"? State by what tissue it

ABSORPTION AND MOVEMENT OF WATER 151

travels in the plant, and describe an experiment proving your statement.
(1897.)

(8) What is the chief function of the wood? Give experimental
evidence in support of your answer. (1891.)

(9) Explain what is meant by "root-pressure." What manifestation
of it occurs in nature? (1892.)

(10) Give an account of the absorbent organs of roots, and of the
process of absorption. (1892. )

(11) The trunk of an Oak tree, when in full leaf, is sawn all round so
deeply as to cut through the sap-wood. State and explain the effect of
this operation. (1893.)

(12) Describe the effect of a tight ligature upon a growing hazel
stem.

(13) What is meant by transpiration? In what circumstances do
plants transpire most? (jive experiments which demonstrate how
transpiration takes place.

(14) Why does a branch when removed from a plant begin to flag?
How may this be prevented ? (1885. )

CHAPTER XII

THE PHYSIOLOGY OF GROWTH AND MOVEMENT

Growth. — The permanent change of form which takes place
in living plants is called growth. The change of size in a dead
seed which takes place when it is placed in water is not a
permanent change, for if the water is removed it returns to its
original size. On the other hand, if a living seed is supplied
with water, the young embryo it contains commences to develop.
Root, stem and leaves are produced, and a permanent change
in shape and size takes place, or in other words, it grows. // is
only living things which can grow.

Conditions which are necessary for Growth.—
i. Heat. The plant and surrounding air must be at a certain
temperature. In winter the temperature of the soil is too low
for absorption to take place, and growth is arrested. The
lowest temperature at which plants can grow is said to be the
minimum temperature of growth. There is a temperature
above which no growth can take place. This cessation of
growth may be caused either by the activity of the protoplasm
being arrested, or by the cells losing water so that they are no
longer turgid. The highest temperature at which plants can
grow is called the maximum temperature of growth. The ex-
tremes of temperature above and below which no growth can
take place vary for different plants. Between the minimum
and maximum temperatures there is one at which plants grow
best ; this is said to be the optimum temperature for growth.

2. Water. — No plant can grow without water, since this
substance enters into the composition of all protoplasm. Water
is also necessary as a medium for carrying nutritive materials to
those parts of the plant where growth is taking place, and it i§

CH. xii PHYSIOLOGY OF GROWTH AND MOVEMENT 153

the means by which the green parts of plants are kept fresh, and
the cells turgid.

3. Oxygen. — Those parts of the plants where growth is
proceeding require oxygen, for without it no energy can be
produced. No growth can take place without energy. Energy
is produced when a plant respires (p. 125).

4. Food Materials. — There must be suitable food materials
present. Food may either be stored up in seeds, or it may be
taken along with water from the soil, or be obtained by the
leaves.

5. Cells in an Embryonic Condition. — The cells of some
parts of the plant must be in such a condition that they can
divide and increase in size.

6. Light. — While light is not absolutely essential for growth,
it is still necessary for healthy growth. Plants will grow faster
in the dark than in the light, as is well seen in the case of
Rhubarb, which when forced in the dark, has small leaves and
long and slender stems. When grown in the light the stem of
Rhubarb is short and thick, and its leaves large. Speaking
generally, it may be said that most plants grown in the dark
have soft stems, which are very much elongated, and of a pale
colour. The leaf-blades, in similar circumstances, are small,
and yellow in colour, and the tissues of the plants have thinner
walls, and contain more water than those grown in the light, or,
light may be said to retard growth.

If wheat seeds are sown too close together so that light cannot
pass between the plants, the stems become long and so slender
that they can no longer support the ears of corn, and the stems
bend under the weight. This constitutes the so-called laying of
wheat. It can be prevented by leaving a sufficient space between
the rows to enable light to pass between the plants, when the
growth will be normal.

The rapid growth of shoots produced from bulbs, tubers,
rhizomes, and seeds is especially valuable, for the light is thus
reached very quickly, and the plants are then capable of in-
dependent nutrition.

Plants grow more rapidly during the night than day. During
the day assimilation goes on and the materials then stored are
used up during darkness in producing a permanent change in
the plant.

154 BOTANY FOR BEGINNERS CHAP.

EXPT. 144. — Fill two plant pots with soil, and sow a few Mustard
seeds in each. Keep the soil moist. Place one pot in a window and
the other in a dark cupboard. Measure the length of the plants in each
pot from time to time. Note —

(i) The plants kept in the dark cupboard are yellow in colour ; those
exposed to light are green.

(ii) Those grown in the dark increase in length nearly three times as
fast as those grown in the light.

(iii) The leaves of the plants grown in the dark are very small, but
those produced in the light are far larger.

(iv) The plants kept in the dark begin to droop and soon die ; those
grown in the light are healthy and strong.

(v) The plants in the dark are often attacked by fungi.

(vi) Light is necessary for the healthy growth of plants, but they
grow faster in the dark.

Growth in Length of Plants.— At the apex of a shoot or
root are two zones of growth. At the extreme apex of the stem
there is a meristematic layer where new cells are produced by
division. Just behind this region the cells 'increase in size, but
little cell division takes place.

Most herbaceous plants from time to time show a change in
the vigour of the growing point. If a plant like the Deadnettle
is examined, the nodes at the base are seen to be crowded to-
gether ; that is, the internodes are short. Higher up the inter-
nodes are longer, while again towards the apex the nodes are
crowded together and the internodes are short. The variation
in the length of the internodes depends upon the strength of the
growing point. At first the growing point is not very vigorous
and it produces short internodes ; as it gains strength, longer
and longer internodes are produced. Later, its strength or
activity again declines, and the internodes become shorter until
the period of growth has ceased. Similarly in the life of most
plants there is a grand period of growth.

Monocotyledonous plants, like the Indian Corn, show this
increase in the vigour of the growing point to perfection. If the
plumule of a germinating seed of Indian Corn be examined it
will be found to be about J of an inch in diameter. If the dia-
meter of a mature stem be measured it will be found to be many
times larger. How has this increase in size been produced ?
The growing point at first could only form a thin stem, but as
its strength increased, a larger and larger stem was produced.
But, here again, the vigour of the growing point declines later in
life and the stem produced has a smaller diameter.

xii PHYSIOLOGY OF GROWTH AND MOVEMENT 155

EXPT. 145. — Obtain a well-developed Deadnettle and examine it.
Note—

(i) The leaves are crowded together at the base and apex ; between
these two regions they are further apart.

(ii) The leaves are produced at the nodes in pairs ; where the inter-
nodes are long the leaves are a greater distance apart.

(iii) That part of the stem where the internodes are longest were
produced during the grand period of growth.

EXPT. 146. — Sow a few seeds of the Indian Corn in a pot. Keep
the soil moist and warm, and exposed to light in a window. Measure
with a tape-measure both the growth in length and thickness of the
seedlings from time to time. Measure and record —

(i) The circumference of the plumule when it first appears above the
ground.

(ii) The length of the plumule when it first appears above the
ground.

(iii) Repeat the above measurements every day during the growth of
the plant.

(iv) Preserve the record of the series of measurements for future
reference.

EXPT. 147. — Germinate a Bean seed, and when the radicle is well-
developed wash it. Measure off half an inch from the tip of the
radicle, and divide it into ten equal parts by marks with Indian ink.
Pass a fish hook through the seed, and suspend it to a cork in a bottle
which contains a little water. Examine at the end of twenty-four hours.
Note—

(i) The amount of growth. Measure from the tip of the radicle to
the mark nearest the base.

(ii) The grand period of growth is well illustrated by the amount of
elongation between mark (3) near the tip and mark (4) from the base.

(iii) The differences in the amount of growth in the different parts
of the root are due to the two zones of growth. The greatest amount of
elongation takes place in the zone where the cells are increasing
in size.

Irritability. — Living protoplasm possesses many properties,
but one of the most important is its power of responding to ex-
ternal stimuli. This property is called irritability or
sensitiveness. The response to these external agencies very
commonly produces movements.

Growing organs possess the property of irritability to a far
greater extent than the older parts of plants. The irritability
of growing organs must be distinguished from the irritability
of mature organs.

156 BOTANY FOR BEGINNERS CHAP.

THE IRRITABILITY OF GROWING ORGANS.

The principal stimuli which act on the growing organs and
produce movements are light, gravitation and water. The
agencies which act on protoplasm, and the movements which
they produce, will here be considered. .

The Action of Light on the direction of Growth.—
The importance of light to plant life cannot be overestimated.
We have seen how necessary it is for assimilation, and for the
healthy growth of a plant. The various parts of plants react in
different ways when exposed to light. The aerial portions
generally turn towards the light, while those parts which under
normal conditions develop in the dark, turn from it. In the
case of the former light is necessary for their full development,
but the latter can grow without light.

Heliotropism.— The action of light is well shown by win-
dow plants. The stems of such plants are not erect as in the
open air, but are inclined towards the source of light. This
turning of a portion of a plant either towards or away from the
light is called heliotropism.

Positive Heliotropism.— The portions of a plant which
turn towards the light are said to be positively heliotropic.
The stems and leaf-stalks incline towards the source of illumin-
ation so as to place their long axis parallel with the rays of
light. But the leaf-blades arrange themselves at right angles to
the illumination and so receive the maximum amount of light.

Negative Heliotropism.— Those parts of the plant which
turn from the light are said to be negatively heliotropic.
Roots, rhizomes, and bulbs turn from the light and are conse-
quently negatively heliotropic. Aerial roots like those of the
Ivy also turn from the light.

EXPT. 148. — Place a pot containing a Castor Oil plant on a window
sill, and observe it from day to day. Note —

(i) The stem and leaf-stalks bend towards the sun ; the divided leaves
arrange themselves at right angles to the window.

(ii) If the pot is turned, the. leaf-stalks and leaf-blades move round
until they occupy their old position.

EXPT. 149. — Examine a piece of Ivy which is clinging to the wall or
to the trunk of a tree. Note —

(i) Most of the clinging roots are developed on theshady side of the stem.
(ii) The roots developed in the light are turned away from it.

Xii PHYSIOLOGY OF GROWTH AND MOVEMENT 157

EXPT. 150. — Obtain a box which will just cover a pot of Musk.
Cover the pot with the box, and so arrange matters that the light from
a window can shine on the plant. Examine in twenty-four hours.
Note—

(i) The plants turn towards the light.

Turn the box so that the light can only shine into one corner.

(ii) On the following day the plants will have turned again to seek
the light.

Turn the box so that the plant can only receive light from the room.

(iii) At the end of another day the plants turn once more to catch the
diffused light.

(iv) Plants like Musk are light-seekers. They always arrange them-
selves so as to receive the maximum amount of light.

Constituents of White Light which Produce
Heliotropism. — If a plant is grown so that the red and
yellow rays of the spectrum (p. 123) can fall on it, there is either
only a little curvature or none at all. But under the influence
of the blue and violet rays nearly as much curvature takes place
as in white light.

EXPT. 151. — Obtain two boxes similar to the one used in Experiment
150. Make grooves in each, so that the open sides of the boxes can
have slips of glass inserted. Germinate three pots of Cress and mark
them A, B, C. Place pot A on a window sill exposed to white light.
Cover B with a box and slide a piece of red glass into position, so that
red rays can only fall on the plants. Cover C with the other box and
slide a piece of blue glass into position, so that blue rays can only pass
to the plants. Note —

(i) The plants in pot A turn towards the window in the same way as
the Musk did.

(ii) The plants in pot B grow erect ; they do not curve in any
direction.

(iii) The plants in pot C curve towards the source of light just as do
the plants in pot A.

Experimental Results.— It must consequently be con-
cluded : —

(1) That plants growing in a window, and more strongly
illuminated on one side than the other, bend towards the source
of light.

(2) That plants which receive only, red rays grow erect, and
do not curve towards the source of light. Or, they grow as
they would in the open air. The rays from the red end of the
spectrum are not instrumental in producing curvature.

158 BOTANY FOR BEGINNERS CHAP.

(3) That plants which receive blue rays bend towards the
side where the strongest light falls, just as plants do which grow
in white light.

(4) That the curvature of positively heliotropic organs is due
to the rays from the blue end of the spectrum.

"Why Heliotropic Movements take Place.— The
movements which plant organs show when acted on by light is
due to the elongation of the side in the shade. Either the side
in the shade grows faster than that exposed to the brighter
light, or a different distribution of water occurs in the cells of
the organs. It must be distinctly understood, that no matter
what the external agency may be which produces the curvature,
it is the protoplasm of the plant cells which responds to it.

Geotropism. — We have seen that most shoots either grow
erect or bend towards the light, but that roots grow away from
the light. There is, however, another external agency in addi-
tion to light, which acts on the various parts of plants. This force
plays a very important part in determining the direction of the
organs of plants and is spoken of as gravitation.1

The property which enables plants to take up a definite position
under the influence of gravitation is called geotropism. Some
organs grow in opposition to the attractive force of the earth,
others grow in the same direction as gravitation acts. As in
the case of heliotropism, we use the terms negative and positive
in describing the two conditions of growth.

Positive Geotropism. — Those parts of plants which grow
towards the centre of the earth are said to be positively
geotropic. Tap roots, aerial roots, and a few cotyledonous
sheaths, grow downwards and are positively geotropic. Lateral
roots and stems grow outwards, and are described as being
diageotropic. In some cases the tap root has become
injured, and one of the secondary roots has developed a posi-
tively geotropic growth.

Negative Geotropism.— All those parts of a plant which
grow upwards or away from the centre of the earth are said to
be negatively geotropic. This is the rule with erect stems,
flower-stems, and a few leaves.

1 As the student will probably know, by gravitation is meant the mutual attraction
between material bodies separated from one another. This mutual attraction between
the earth and bodies near it gives rise to the weight of bodies.

xii PHYSIOLOGY OF GROWTH AND MOVEMENT 159

EXPT. 152. — Germinate a few Peas in damp sawdust. Place one on
damp soil. Place another with the radicle and plumule in a horizontal
position on a piece of
glass which is covered
with damp blotting
paper. Note —

(i) The radicle of
the Pea in the damp
soil bends downwards
and the plumule up-
wards.

(ii) The plumule of
the Pea on the piece
of glass grows straight
upwards, but the root
grows along the piece
of glass until it reaches
the edge, when it turns
so as to make nearly a
right angle with the
rest of the root, and
then grow down-
wards.

(iii) This shows that
the root is positively
geotropic and the stem
negatively geotropic.

EXPT. 153.— Make
a hole in the bottom
of a glass tumbler for
drainage. This can
be done by striking a
blow at the centre
with a sharp pick.
The tumbler may
crack, but if it holds
together anyhow it
will do. Fill with
soil (p. 13). and put a
quick growing plant
in it. Expose to light.
Note—

(i) No roots will be

seen near the glass (Fig. 162), or, if they should appear there, they will
soon bend away from the light.

Cover the tumbler with brown paper to prevent the light from affect
ing the roots. Examine in a few days.

(ii) The soil near the glass is packed full of roots.

(iii) If the plant and soil are turned out, and a sharp knife is used to

FIG. 162. — Photograph of a plant grown in a tumbler to
show the distribution of the roots. The white roots
are close to the side of the tumbler. During the
growth of the plant the tumbler was covered with
brown paper. The plant produced both flowers and
fruits.

160 BOTANY FOR BEGINNERS CHAP.

cut a slice of soil away near the centre, it will be found full of roots with
the tap-root growing downwards.

(iv) This shows that the ordinary roots are negatively heliotropic and
the tap-root is positively geotropic.

Hydrotropism. — It has already been seen (p. 59) that
roots growing in dry soil are attracted by moisture. The move-
ment of any part of a plant towards moisture is termed hydro-
tropism, and roots possess this property to a far greater extent
than the other organs of plants.

Movements Caused by Contact.— Just as animal bodies
respond to contact so do the organs of a few plants. This is
well shown in the case of climbing organs (p. 26). When a
tendril comes in contact with a solid body the side of the tendril
touching the object has its growth arrested, while the side
away from the object grows more quickly. This produces an
elongation of the side away from the object and causes the
tendril to curve and twine round the object.

THE IRRITABILITY OF MATURE ORGANS.

Special Cases. — Most full grown organs are incapable of
moving, but the organs of a few plants are endowed with the
power of vigorous movement. These movements are due to
changes in the amount of water which the cells of the organs
contain. When cells are full of water, it presses on the elastic
walls and they become greatly distended, their cavities becom-
ing enlarged. If the cells lose water, the walls shrink and the
cavities are diminished. It is to the changes in the size of the
cells of an organ that the movements under consideration are
due.

The amount of water in the cells depends upon the temperature
and amount of light which they receive. The change in the
position of leaves and the opening and closing of flowers are
due to changes in the turgidity of the cells on different sides of
the leaf. The turgidity, depending as it does upon the amount
of water absorbed, is evidently produced by the amount of
light and by the temperature. Many flowers and leaves show a
periodic movement.

The Opening and Closing of Flowers. — Many flowers
and some inflorescences (p. 1 56) change their position from day

xii PHYSIOLOGY OF GROWTH AND MOVEMENT 161

to night. It is a general rule that flowers are open during light
and closed at night ; but a few open at night and close during
the day. The closing of the flowers during darkness is called
the sleep of the flowers.

EXPT. 154. — Collect a few flowers of the Dandelion, and place them
in a tin box so that they receive no light. Note —

(i) At the end of an hour they are all closed up.

Now place their cut ends in water and expose them to a bright light,

(ii) They will open again.

This shows that the amount of light which they receive causes them
to open and close.

EXPT. 155. — Bring a Tulip plant with fully developed flowers, which
are closed, into a warm room. Note —

(i) If the temperature of the room is about ten degrees Fahrenheit
higher than the external air whence the plant was obtained, the flowers
open.

Now expose the flowers to a lower temperature, either by placing
them outside in the cold, or by surrounding the pot with a mixture of
salt and ice.

(ii) The flowers will close. The closing of the flowers is due to the
decrease in the amount of heat which they receive.

The Sleep of Leaves.— If the compound leaves of the
Wood Sorrel or Clover are examined during early morning they
are found to be folded so as to expose the least amount of sur-
face to the atmosphere. If the same leaves are noticed at noon
they will be seen to be fully expanded.

The Utility of Plant Movements.— The heliotropic
and geotropic movements of organs place them in the most
favourable position for performing their functions.

Thus, when leaves are placed at right angles to the rays of
light, they receive the maximum amount of light and energy,
and are thus able to assimilate to perfection. The primary
root being positively geotropic, carries the secondary roots into
new soil from which food is obtained. The primary stem grow-
ing erect, places the aerial organs in a good position for receiving
light. The roots being both geotropic and hydrotropic, they
are placed in a good position to obtain food, and to fix the plant
firmly in the soil. The flowers close at night to protect the
internal organs from losing heat by radiation, and to prevent
them from being washed by rain and dew. They open in warm
sunshine so that insects can visit them, and close in the cold to
prevent loss of heat. Those flowers which open during dark-
ness and close during light are visited by night-flying insects.

162 BOTANY FOR BEGINNERS CHAP.

The change from the diurnal to the nocturnal position, which
many leaves undergo, protects them from rain, snow, hail,
changes in temperature, and prevents loss of heat by radiation.
The leaves are folded so as to expose the minimum amount of
surface to the air during their nocturnal position, and during the
diurnal as much surface as possible is exposed for assimilation.

SUMMARY.

Growth means a permanent change of form. It is only living things
which grow.

Conditions necessary for Growth. — ( i ) A certain temperature which
varies for different plants. For every plant there is a minimum tem-
perature below which no growth can take place, and a maximum above
which growth will be arrested. Between these points the optimum
temperature occurs.

(2) Moisttire must be present, because it enters into the composition
of the protoplasm.

(3) Oxygen is necessary for most plants.

(4) Suitable food materials must be present.

(5) Light is necessary for the healthy growth of all green plants.
Light prevents too rapid growth.

Irritability means the property of protoplasm to respond to external
influences. Most growing and some mature organs possess this property.
Light, gravitation, and moisture are the principal agents which produce
movements in growing plants.

The Action of Light on Growing Organs. — Heliotropism refers to
the power of turning either towards the light or away from it which
plants possess. Most shoots bend towards the light and are said to be
positively heliotropic. Roots, rhizomes, and bulbs turn from the light
and are said to be negatively heliotropic.

Heliotropic movements take place as a result of changes in the
length of one side of the organ in comparison to the other. This
produces curvature.

Geotropism is the property which enables the organs of plants to
take up a definite position in regard to gravitation.

Movements caused by Contact. — When a tendril comes in contact
with a support, the side which touches it has its growth arrested, and
the opposite side grows more quickly. This causes curvature, and
enables the tendril to twine round the support.

The Sleep of Flowers and Leaves. — Many flowers and leaves change
their position from day to night. The movements are produced by
changes in the amount of water which the cells of the various parts of
foliage leaves or floral leaves contain.

The Utility of the Movements.— All the movements which the various
parts of plants perform are to bring the plants into touch with their
surroundings.

PHYSIOLOGY OF GROWTH AND MOVEMENT 163

QUESTIONS ON CHAPTER XII.

(1) Define the term growth. What conditions are necessary for
growth ?

(2) Why does Rhubarb grow faster in the dark than in the light ?

(3) Give an account of an experiment which proves that plants
grow faster in the dark than in the light.

(4) Explain, and illustrate by an experiment what is meant by " a
grand period of growth " in the life of a plant.

(5) The protoplasm is said to possess the property of irritability.
Explain this.

(6) Why do the stems and leaves of window plants take up a definite
position with regard to the light ?

(7) Explain the term heliotropism. Aerial stems are said to be
positively heliotropic and roots negatively heliotropic. Explain this.

(8) A plant is covered with a blue glass. How will its method of
growth differ from one grown under red glass ?

(9) Explain why it is that, when a seed germinates, the stem grows
upwards and the root downwards. (1889 and 1897.)

(10) Describe, and briefly explain, the influence of light upon the
direction of growth of stems and of roots. (1891.)

( 1 1 ) What is the effect of light upon the direction of growth of stems
and leaves? (1896.)

(12) Most flowers are open in the light and closed during darkness.
Explain how this change is produced, and of what service it is to the
flower.

M 2

CHAPTER XIII

FLOWER AND INFLORESCENCES

Floral Leaves.— In addition to the foliage leaves p. 31),
stipules (p. 45), and bracts (p. 46), which have already been
dealt with, certain modified leaves which go to build up the
flowers of a flowering plant, and are called floral leaves, now

call for considera-
tion. The succes-
sive whorls or rings
of floral leaves are,
commencing with
the external whorl,
as follows.

i. — The Calyx,
built up of separate
leaves which re-
ceive the name of
sepals. Each sepal
is a modified leaf
and is, as a general
rule, green.

2. — The Corolla,
built up of petals.
Each petal is also a

modified leaf, which may be brightly coloured and of a peculiar
shape.

3. — The Andrcecium is built up of stamens which form the
male organs of reproduction and produce a substance called
pollen. Each stamen is, like a sepal and petal, a modified leaf ; it

FIG. 163. — Diagram of Flower in longitudinal section.
Ar, calyx ; c, corolla ; a, androecium ; g, gynoecium.
(S.)

CH. xin FLOWER AND INFLORESCENCES 165

performs a special work in connection with the reproduction
of plants.

4. — The Gyncecium, or pistil, is built up of carpels. The
pistil constitutes the female organ of reproduction and always
occupies the centre of the flower. It produces ovules, which
under healthy conditions form the future seeds. The following
experiments will make clear what is meant by floral leaves.

EXPT. 156. — Examine a Wallflower. Note —

(i) The calyx on the outside of the flower. In this case it is built up
of four sepals, each of which is long and hairy. The two inner sepals
are swollen at the base. Each sepal, which is either yellowish or
brownish-red in colour, can be pulled off without tearing it from its
fellows.

(ii) Standing just within the calyx, and alternating with the sepals,
four yellow or reddish-brown leaves will be found. These form the
corolla. The petals are arranged in the form of a cross and are the
largest leaves of the flower.

(iii) Within the corolla six stamens occur. Four are long and two
short. Remove one : it consists of (a) a stalk, called a filament ; (b) a
head — the anther. Open the anther : it contains a number of micro-
scopic pollen grains.

(iv) The centre of the flower is occupied by two carpels joined to-
gether, which form the pistil, and is divided at the apex into two lobes.
The long somewhat swollen body forming the lower part of the pistil
is called the ovary. The lobes at the apex of the ovary form the
styles^ and the tips of these form the stigmas.

(v) Open the ovary : a number of rounded bodies are seen — the
ovules.

EXPT. 157. — Examine the flower of a Buttercup. Note —

(i) The five sepals (green and leaf-like in appearance) on the outside
forming the calyx.

(ii) Five yellow petals, constituting the corolla, are found just within
the calyx, filling the gaps between the sepals.

(iii) A number of yellow stamens, each consisting of a filament and an
anther. The anthers, if ripe, are full of pollen.

(iv) Many small green carpels — not united together as in the wall-
flower— make up the pistiL Each carpel possesses at its base a swollen
portion — the ovary — and above this the style and stigma can be dis-
tinguished.

(v) In each ovary a small egg-shaped ovule is to be found.

Flower. — The following reasons lead us to believe that a
flower is a modified shoot.

i. — The flowers are produced either at the apex of a shoot or
in the axil of foliage leaves. This is just the position in which
we find branches or shoots (p. 16).

1 66 BOTANY FOR BEGINNERS CHAP.

2. — The floral leaves are arranged either in a lateral (p. 17)
or in a spiral (p. 37) manner. This is just what we find in the
case of foliage leaves (p. 36-7).

3. — The floral leaves are very often leaf-like in form, markings,
and colour.

4. — In many cases the intermediate forms between floral
leaves and foliage leaves can be seen on one plant. Thus, in
the White Water-Lily there are numerous intermediate forms
between carpels, stamens, petals, and sepals. In the Christmas
Rose, too, all the various stages between foliage leaves and
carpels can be made out.

5. — Under cultivation, or change ot surroundings, the floral
leaves may become changed. Thus, in the cultivated Rose, the
stamens and carpels have been converted into petals. In some
cases wild flowers can be collected possessing green leaves
instead of carpels.

A flower is a branch which has become modified for the
special work of producing seeds for the reproduction of its
kind.

Inflorescence. — An inflorescence is a collection of flowers
produced from a common stalk. The common stalk upon
which the flowers are borne is called a peduncle or rachis.
(Fig. 164). If the flowers possess stalks which connect them
to the peduncle the stalks are called pedicels. When the
flowers spring from the peduncle without stalks they are said to
be sessile.

Many inflorescences are produced in the axils of leaves,
when they are said to be axillary. When found at the apex
of a shoot the flower is said to be terminal.

Indefinite Inflorescences. — If the flowers at the base of
an inflorescence open first, as in the Wallflower and Lily of the
Valley, the inflorescence is called indefinite. In such an
inflorescence the apex keeps on producing flowers, and we
cannot tell where it is going to stop flowering.

Spike. — There are a number of such indefinite inflor-
escences, all bearing a certain relation to one another. When
the flowers are arranged on the peduncle in a sessile manner,
/.<?., without pedicels, the inflorescence is said to be a spike.
Examples — Ribgrass or Plantain, Bistort, and Verbena.
(Fig. 165).

XIII

FLOWER AND INFLORESCENCES

167

Raceme. — When the flowers are connected to the peduncle
by pedicels they form a raceme. This is a very common form

s c

FTG 164 — Diagram of Indefinite Inflorescences. A, panicle ; B, raceme ; C, spike ;
D, umbel ; £, head. (S.)

FIG. 165.— Spike of FIG. 1 66. — Raceme of FIG. 167.— Panicle of Oats.
Bistort. (One- Wild Hyacinth. (One (Reduced.)

tenth nat. size.) tenth nat. size.)

of inflorescence. Examples — Wallflower, Foxglove, and
Hyacinth. (Fig. 166).

1 68 BOTANY FOR BEGINNERS CHAP.

Panicle. — When the pedicels themselves branch, so that
there are two or more flowers produced from a single pedicel,
& panicle is formed. Examples — Rhubarb, Oats. (Fig. 167).

Corymb. — When the pedicels are produced at different
levels, and are of different lengths, all the flowers being thus
brought to the same level, the inflorescence is called a corymb.
Example— Candy Tuft. (Fig. 168).

Simple Umbel. — If all the pedicels spring from the same
point of the peduncle and the flowers are brought to the same

A B

FIG. 168.— A, Corymb of Candy Tuft ; FIG. 169.— Simple umbel of Cowslip.
B, section of. (One-fifth nat. size.)

level, a simple umbel is formed. Examples — Cherry and
Cowslip. (Fig. 169).

Compound Umbel. — If all the pedicels spring from the
same point of the peduncle, and branch so as to bring all the
flowers to the same level, the inflorescence is known as a
compound umbel. Examples— Fool's Parsley, Carrot, and Hem-
lock. (Fig. 170).

Head or Capitulum.— An inflorescence in which the
peduncle is shortened and flattened out, and the flowers are
fixed to it either by pedicels or are sessile, is called a head or
capitulum. The flattened-out peduncle is called a common

FLOWER AND INFLORESCENCES

169

receptacle. The capitulum is very common in the order of
plants called the Compositae. The florets of the head open on
the outside first, the inner ones opening last. Examples — Daisy,
Dandelion, and Clover. (Fig. 172).

FIG. 170. — Compound
umbel of Sweet
Cicely.

FIG. 171. — Enlarged
view of portion of
compound umbel
of Sweet Cicely

FIG. 172.— Head of Clover.
(One-fifth nat. size.)

EXPT. 158. — Examine the inflorescence of the Wallflower. Note —
(i) The peduncle, or axis upon which the flowers are placed,
(ii) The pedicels by which the flowers are connected to the peduncle,
(iii) The kind of inflorescence. The pedicels spring from different
parts of the peduncle and thus form a raceme.

EXPT. 159. — Obtain a Plantain and examine it. Note —

(i) The large number of green flowers which hide the peduncle from
view.

(ii) The flowers do not possess stalks, or are sessile on the peduncle.

(iii) The arrangement of the sessile flowers shows that the inflorescence
is a spike.

EXPT. 160. — Strip off the flowers from an inflorescence of the Daisy.
Note —

(i) The common receptacle upon which the flowers are placed,
(ii) The flowers are sessile, as in the spike,
(iii) The inflorescence is a head or capitulum.

EXPT. 161. — Compare the simple umbel of the Cowslip or Oxlip
with the compound umbel of the Fool's Parsley. Note —

(i) In the simple umbel of the Cowslip the pedicels are not branched,
while in the compound umbel of Fool's Parsley each pedicel is branched ;
and at the apex of each branch a flower is produced.

(ii) The flowers in both come to the same level.

170

BOTANY FOR BEGINNERS

CHAP.

Other Indefinite Inflorescences.— There are a few more
indefinite inflorescences which remain to be considered.

Spadix. — The spadix is a spike of male and female flowers.
The peduncle is fleshy and is continued for a distance above the
place where the flowers are inserted. It is enclosed by a large

sp
.-st

FIG. 173. — A, Arum (one-fourth nat. size). B, Spadix of Arum, with the front of
spathe cut away. C, Spadix, with the whole of the spathe cut away ; S, spathe ;
sp. spadix ; F, female flowers ; M, male flowers ; st, undeveloped male flowers.

leaf called the spathe, which in the wild form is green, but in a
cultivated state is white. Example — Arum. (Fig. 173).

Catkin. — The catkin is a crowded spike of inconspicuous
sessile male or female flowers. When it consists of male flowers
alone, it droos off after flowering. The male flowers of the Oak,

xiii FLOWER AND INFLORESCENCES 171

Hazel, and Sweet Chestnut are arranged in catkins. Both the
male and female flowers of the Willow, Poplar, and Birch form
catkins.

EXPT. 162. — In either April or May obtain an Arum and examine it.
Note—

(i) The yellowish-green spathe which surrounds the spadix. It is
longer than the spadix.

(ii) Cut away the spathe. Notice the inside is, as a rule, full of small
flies. The spadix, which is thick and fleshy, is seen within and is
generally of a purple colour above the flowers.

(iii) The female flowers are at the base of the spadix and the male
flowers are just above these. There is a ring of undeveloped male
flowers just above the fertile male flowers.

EXPT. 163. — Collect a few catkins of the Hazel. They are produced
in the months of February and March. Examine one. Note —

(i) The external appearances of the inflorescence. It is pendulous.

(ii) Remove a single flower with a pin. Observe each flower is
connected by a very short stalk or is sessile on the peduncle. Only
stamens are found in each flower.

(iii) The inflorescence is a spike of male flowers.

Relation between Indefinite Inflorescences.— The

raceme only differs from a spike in having pedicels which sepa-
rate the flowers, so that they make a better show and are more
likely to be seen by insects than the sessile flowers on a spike.

The panicle, which is a compound raceme, generally bears
only small flowers, and the arrangement of these on the ends
of small stalks causes them to be seen for a great distance. It
differs from both the spike and raceme ; from the former in
possessing stalks, and from the latter in having these branched.

The corymb differs from the raceme in having the pedicels of
unequal length, and in the flowers being all brought to the same
level. Thus, a more or less flat surface, upon which insects love
to rest and collect honey, is formed.

In the head the same result is obtained by the flowers being
crowded together on a flat receptacle, an arrangement which
also makes them very conspicuous.

Both the catkin and the spadix are spikes ; the former is a
catkin of male flowers, while the latter bears both male and
female flowers. The catkins are produced before the leaves,
and by their pendulous position aid in the distribution of the
pollen by the wind.

172

BOTANY FOR BEGINNERS

CHAP.

Definite Inflorescences. — A definite inflorescence is one
where the uppermost flower opens first and the lower ones in

FIG. 174.— Diagram of definite inflorescences. A, dichotomous cyme ; B, helicoid
cyme ; C, scorpioid cyme.

regular order, beginning at the top. In such an inflorescence it
is possible to say where the flowering will cease. Such inflores-
cences are also called cymose. As a rule the apex of the shoot

produces a flower, which deve-
lops first, the flowering being
continued by secondary or ter-
tiary branches. The following
are the principal forms of de-
finite inflorescences.

Solitary Flowers.— In the
few cases where the apex of the
peduncle produces a single
flower, the flower is said to be
solitary. Example — Tulip.

The solitary flower may be
produced in the axil of a leaf,
when it is said to be solitary
and axillary. Example — Poor
FIG. 175.- Axillary flowers of Ground Man's Weather - glass, and

Ivy. (One-fourth nat. size.) Ground Ivy. (Fig. 175.)

Dichotomous Cyme.— In

the dichotomous cyme the apex of the peduncle is occupied by
a flower, which opens first. From beneath this flower new
branches are produced, and the apex of each branch also

XIII

FLOWER AND INFLORESCENCES

173

produces a flower. Thus, in a dichotomous cyme each apical
growing point eventually produces a flower. Examples — Stitch-
wort and Sandwort. (Fig. 176.)

Scorpioid Cyme.— When the cyme is developed on one side
only of the peduncle, and is in the young state rolled up in

FIG. 176.— Dichotomous cyme of the Stitchwort. T, terminal flower ; L, lateral

flower.

a spiral manner, it is called a scorpioid cyme. Example — For-
get-me-not. (Fig. 177.)

Verticillaster. — If the flowers are produced on opposite
sides of the stem, in the axils of leaves, and they stand tier above
tier, the inflorescence is called a vertitillaster. Some botanists
call it a whorled inflorescence, but if it is examined with care
the flowers will be seen to grow from the axils of leaves, and
only appear to be whorled. Example — Deadnettle. (Fig. 178.)

174

BOTANY FOR BEGINNERS

CHAP.

Glomerule.— When the flowers belonging to a number of
cymes are crowded and rolled together so as to form a head,
the inflorescence is called a glomerule. Examples— Nettle, Box,
Valerianella.

FIG. 177. — Scorpioid cyme of Forget-
me-not. (Half nat. size.)

FIG. 178.— Verticillaster of the Dead-
nettle.

EXPT. 164. — Collect the inflorescence of the Stitch wort (it flowers
from April to August) and examine it. Note —

(i) The main axis produces a flower, and from beneath this the
branches are produced.

(ii) The branches also produce flowers, new ones being formed from
beneath these.

(iii) The branching is dichotomous, i.e., in a forked manner, and the
inflorescence is a dichotomous cyme.

EXPT. 165. — Obtain a Deadnettle when in flower. Note —

(i) The way in which the flower springs from the axil of opposite
leaves.

(ii) Each pair of leaves produces flowers, those in the lower ones
opening first.

(iii) The inflorescence is a verticillaster.

Relation between the Definite Inflorescences. —

The variation in the different kinds of inflorescences depends
upon the mode of branching of the shoot. This is shown
in the dichotomous cyme of the Stitchwort. In the Forget-me-
not the axis is produced from lateral buds, the apical buds in
each case producing a flower. The lateral buds only develop
on one side. Thus, the scorpioid cyme of the Forget-me-not

XIII

FLOWER AND INFLORESCENCES

'75

differs from the dichotomous cyme in which the lateral buds
produce branches on both sides of the apex. In the glomerule
the branching brings the flowers to the same level and appears
to form a head.

Bracts.— The bracts are borne upon the inflorescence (p. 46).
They are leaves in the axils of which the flowers are produced.

FIG. 179. — Two views of in-
volucre of Daisy. R, ray
flowers ; M, bracts of
involucre.

There may be one

large bract only,

which surrounds

the inflorescence as

the spathe of the

Arum. (Fig. 173.)

In some cases these

bracts are brightly

coloured. Very

small bracts are

often found at the base of each pedicel, as in the Hyacinth,

when they are termed bracteoles.

Involucre. — When the bracts are arranged around the
flowers in a whorl, as in the Daisy and Dandelion, they form an
involucre. (Fig. 179.) The bracts of the involucre may be
leafy, scaly, or partly leafy and scaly. They may be imbricated
like the tiles on a house, or simple.

The Anemone has an involucre of three bracts, just below the
flower. (Fig. 180.)

FIG. 180.— A, Anemone ; B, involucre ; M, M, M,
bracts of involucre ; F, flower.

i;6 BOTANY FOR BEGINNERS CHAP.

SUMMARY.

Floral leaves are modified leaves which build up the flowers.
They form a number of whorls, as follows —

(1) The sepals, which form the calyx.

(2) The petals, which form the corolla.

1(3) The andrcecium, or male organs of reproduction, is built up of
stamens.

(4) The gynoecium (pistil), or female organ of reproduction, is built
up of carpels.

Stamens consist of a stalk — \h& filament, and a head — the anther.

Pistils are built up of one or more carpels ; they consist of ovary,
style, and stigma.

The Flower is supposed to be a modified shoot or branch, for the
following reasons—

1 i ) The flowers are produced in the same positions as the buds, viz. ,
at the apex of the main shoot and in the axils of leaves.

(2) The floral leaves are arranged either in a lateral or spiral manner.

(3) The floral leaves may be leaf-like.

(4) The intermediate forms between foliage leaves and the various
kinds of floral leaves are known.

(5) The floral leaves change under cultivation.

An inflorescence is a collection of flowers produced from a common
stalk. The common stalk upon which the flowers are borne is called
a peduncle, and the smaller stalks by which the flowers are attached to
it are termed pedicels. There are twro kinds of inflorescences, (a) in-
definite, (b) definite.

Indefinite inflorescences. — The -flowers open at the base first and
at the top last.

Definite inflorescence. — The top flower opens first.

Indefinite inflorescences are — Spike, Raceme, Panicle, Corymb, Simple
Umbel, Compound Umbel, Capitulum, Spadix, Catkin.

Definite inflorescence are — Solitary, Dichotomous Cyme, Verjicillaster,
Glomerule.

Bracts are greatly modified leaves in the axil of which the flowers
are produced. When the bract is large and surrounds the inflorescence
it is called a spathe. An involucre is a collection of bracts which
generally enclose the flowers of the inflorescence.

QUESTIONS ON CHAPTER XIII.

(1) Distinguish between a "flower" and an "inflorescence." Illus-
trate your answer by reference to the Daisy. (1897).

(2) Explain, with examples, the following terms — bracts, stipules,
petiole, peduncle. (1896.)

(3) What is a flower ? What structures compose it ?

(4) Explain the differences between definite and indefinite inflores-
cences, giving examples of each.

xiii FLOWER AND INFLORESCENCES 177

(5) Give examples of the following kinds of inflorescences, and ex-
plain their relation to each other — spike, raceme, panicle, head, umbel.
(1890.)

(6) Describe and compare the inflorescences of the Wallflower,
Parsley, and Daisy. ( 1 893. )

(7) Briefly describe, giving examples, the following forms of in-
florescences, and point out the relation which exists between them —
Spike, Spadix, Catkin.

(8) Fully describe the inflorescence of any three of the following
plants— Chickweed (Stellaria), Wallflower (Cheiranthus), Forget-me-not
(Myosotis), Deadnettle (Lamium), Foxglove (Digitalis). (1891.)

(9) Describe the inflorescence of the Arum.

(10) What is an involucre? What plants possess involucres?

( 1 1 ) Explain how a bracteole differs from a spathe.

CHAPTER XIV.

THE TERMS USED IN DESCRIBING THE FLOWER

•

Terms. — In describing the structure of a flower it is necessary
to use a number of terms or names to define the appearances
which the organs of a flower may present. It must be distinctly
understood that the mere learning of such terms without knowing
how to apply them is of little use. In all cases the flowers them-
selves should be examined and their peculiarities of structure
noted. The principal terms used in describing the flower are : —

The Torus. — The upper portion of the flower stalk upon
which the floral leaves are fixed is called the torus or receptacle.
It is usually thicker than the portion below, and may expand
between the stamens and the pistil into a disc. The disc may
be club- cup- or urn-shaped. Upon the shape of the receptacle
will depend the appearance of the flower.

Complete and Incomplete Flowers. -If the flower
is built up of calyx, corolla, stamens, and pistil, it is said to be
complete. When one or more of these parts are absent the flower
is said to be incomplete.

The Buttercup, Wallflower, and Primrose are examples of
complete, and the Anemone, Hazel, and Oak of incomplete
flowers.

Perfect and Imperfect Flowers.— When the flower pos-
sesses both stamens and pistil it is said to be perfect. The
Anemone, Pea, and Rose are examples of perfect flowers. If
either the stamens or pistil is absent the flower is said to be
imperfect. The Hazel, Dog's Mercury, and Oak are examples of
imperfect flowers.

Regular and Irregular Flowers.— When the flower can

CH. xiv TERMS USED IN DESCRIBING THE FLOWER 179

be divided into equal halves in any plane, it is said to be regular
or actinomorphic. If the flowers of the Hyacinth and Wallflower
are examined they are seen to be regular or actinomorphic, for
if a sharp knife is used they can be cut into equal halves in any

FIG. 181. — Female flowers
Dog's Mercury.

FIG. 182.— Actinomorphic flower of the Primrose
the dotted lines show the planes of division.

FIG. 183.— Zygomorphic flower of the Pea ; the dotted lines show the plane of
division.

plane which passes through the centre of the flowers. (Fig. 182).
The flowers of the Pea and Deadnettle can only be divided into
equal halves in one plane. Flowers of this kind are said to
be irregular or zygomorphic (Fig. 183). If a flower cannot be

N 2

i8o

BOTANY FOR BEGINNERS

CHAP.

divided into equal halves in any plane it is said to be asym-
metrical, as in a few plants which belong to the Pink family.

The portion of the flower which faces the bract in the axil or
which it stands is called the anterior part ; while the portion
which faces the axis of the inflorescence is the posterior part.
The plane which passes through the flower in such a way as to
divide it into oosterior and anterior halves is called the trans-
verse one, and that which
passes through the middle
of the bract and axis of
the inflorescence is said
to be the median plane.

EXPT. 1 66. — Obtain a
flower of the Gorse or
Laburnum and examine it.
Note—

(i) The large petal which
receives the name of the
standard is posterior, be-
cause it is the nearest to the
axis of the inflorescence.

(ii) The two petals which
slightly adhere, and are
called the keel, are anterior,
because they are the nearest
to the bracts.

(iii) The two petals, one
on each side of the stan-
dard, receive the name of
wings ; they are lateral, i.e.,
at the sides.

(iv) The flower is irregu-
lar, or zygomorphic, because

there is only one plane along which a section can be made to divide
it into equal halves. This plane passes through the centre of the
standard and between the petals of the keel.

EXPT. 167. — If the flower of the Apple or Blackberry can be ob-
tained, examine it. Note —

(i) The flower consists of five sepals and five petals,
(ii) It can be divided into equal halves in any plane, therefore
it is regular or actinomorphic.

Shape of Flower. — There are a number of terms which are
used in describing the shape of the flower. It is said to be —

I. — Cruciform, when the petals are arranged in the form of a
cross, as in the Wallflower and Cabbage. (Fig. 185).

FIG. 184. — A, Raceme of Laburnum ; st, stan-
dard ; w, wings; k, keel, i, 2, 3, the
flower from different points of view.

xiv TERMS USED IN DESCRIBING THE FLOWER 181

2. — Papilionaceous, when butterfly-shaped as in the Pea and
Gorse. (Fig. 186).

3. — Spurred, when a spur is formed either from the corolla or
calyx. This spur may be used for storing up honey. Examples
— Monkshood, and Toadflax. (Fig. 187).

4. — Tubular, when a tube is formed as in the florets of the
Thistle. (Fig. 188).

FIG. 185. FIG. 186. FIG. 187. FIG. 188.

Cruciform flower. Papilionaceous flower. Spurred flower. Tubular flower.

5. — Rotate, when the tube of the flower is short and the lobes
flat and spreading, so that it resembles a wheel. Examples —
Potato, and Forget-me-not. (Fig. 189).

6. — Funnel-shaped, when it is shaped like an inverted cone, as
in the Convolvulus. (Fig. 190).

FIG. 190.

Funnel-shaped

flower.

FIG.. 191.
Ligulate flower.

FIG. 192.

Campanulate

flower.

7. — Ligulate, when strap-shaped, as the floret of the Dande-
lion. (Fig. 191).

8. — Campanulate, when bell-shaped, as in the Harebell and
Clustered Bluebell. CFig. 192).

1 82

BOTANY FOR BEGINNERS

CHAP.

9. — Personate, when the throat of the flower is masked, as in
the Snap-dragon. (Fig. 193).

10. — Labiate, when the flower is two-lipped, as in the Dead-
nettle and Sage. (,Fig. 194).

Size of Flower. — The flowers may be very small, so that it
is necessary to use a hand-lens to make out their different parts,
or they may be large. If a plant bears small flowers, it is the
rule for a large number to be produced. When large flowers
are produced by a plant, only a .-Stigma

few are formed. The diameter ^^&\<Z3Z^ J

of the flower should be given
when describing it, For instance
the diameter of the flower of
the Wallflower is given as

FIG. 193.
Personate flower.

FIG. 194.
Labiate flower.

FIG. 195. — A longitudinal section of the
flower of the Daffodil ; showing inferior
ovary and superior perianth.

inches ; while the flower of the Fool's Parsley is J of an inch in
diameter.

Colour. — In describing a flower its colour must always be
noted. Some flowers are green, others are brightly coloured.
The Wallflower is yellow or reddish brown, the Hare-bell is
blue, the Apple blossom varies from white to pink, and the
Anemone is generally white. If the flower possesses any pecu-
liarities such as markings, hairs, &c., they must be described.

Perfume. — Those flowers which are visited by insects may
be sweet-scented or without perfume. Green flo-wers, as a rule,
have no perfume, but if the flowers open at night they are very
sweet scented. The characters of the flowers as to perfume,
must be recorded when writing the description of the flower.

Cohesion and Adhesion. — The term cohesion is used

TERMS USED IN DESCRIBING THE FLOWER 183

Stiyma

to note union between similar members, as sepal to sepal or
petal to petal. Adhesion is used to note union between dissimi-
lar members, as sepals to petals, stamens to petals, £c.

Calyx.— The sepals which form the calyx may be separated
from each other, or may grow together by their edges to
form a cup. If the sepals are distinct, as in the calyx of the
Buttercup, the calyx is said to be polysepalous. (Fig. 163). If
the sepals are united so as to form a cup the calyx is gamose-
palous, as in the
Deadnettle and
Primrose. (Fig.
182).

When the ca-
lyx is fixed below
the pistil it is
inferior, as in
the Wallflower
and Buttercup.
(Fig. 163). If the
calyx is above
the pistil it is
superior, as in
the Currant and
Parsley. (Fig.

195)-

The number
of the sepals is
noted and the
number of
whorls they

make. In the gamosepalous calyx the number of the sepals
can be inferred from the number of the divisions to be
made out. If there are five lobes to the calyx it is a five-lobed
calyx, as in the Primrose and Toadflax. The number of rows
of the sepals must also be noted in describing the calyx. There
may only be one row, as in the Buttercup, or two, as in the
Wallflower. The shape of the sepals or lobes of the calyx is of
importance. The sepals may be shaped like the leaves, (p. 38-40),
and the same terms are used in describing both. The limb or
free portion of the calyx may be entire, toothed, or lobed. The

Perianth

FIG. 196. — A longitudinal section of the flower of the White
Lily ; showing superior ovary and inferior perianth.

i84

BOTANY FOR BEGINNERS

CHAP.

lobes may be shaped like the tips of the leaves, (p. 44), and the
same terms are used as in describing leaves.

The colour of the calyx and whether it is hairy or smooth,
must be recorded. If the calyx is coloured it is said to be
petaloid) as in the Christmas Rose and Anemone. In most cases
it is green.

The function of the calyx is to protect the stamens and pistil
from injury. In those cases where it is coloured it serves to
attract insects. It may persist after those functions are per-
formed, as in the Dandelion, where it persists as a pappus
(Fig. 197) of hairs which aids in the
distribution of the seeds by the action of
the wind. In the Poppy the sepals fall
off when the flower opens. The calyx
may take part in forming the fruit, as in
the Apple and Pear.

Corolla. — If the petals are united, as
in the Primrose, a gamopetalons corolla
is formed. In its simplest form the
corolla consists of a number of separated
petals, and it is polypetalous, as in the
Buttercup, Wallflower, and Stitchwort.

When the corolla springs from beneath
the pistil and from the thalamus, as
the receptacle is sometimes called,
in the Wallflower, Rock Cress, and

FIG. 197.— Pappus of
Dandelion.

it is hypogynous^ as
Poppy.

If the petals are fixed on the calyx the corolla is perigynous,
as in the Pea, Rose and Apple.

[If the flower has the corolla and stamens hypogynous, it is a
hypogynous flower ; if the corolla and stamens are perigynous,
it is a perigynous flower ; and when both corolla and stamens are
inserted on the ovary it is an epigynous flower.]

The corolla may spring from the top of the ovary, when it is
said to be epigynous, as in the Cow-Parsnip and Sea Holly.

The number of the petals or the lobes of the corolla, the shape
of the petals, or the lobes, must be observed and the terms used
for the calyx may be employed to describe them.

Androecium. — The whole collection of stamens of a flower
constitute the androecium. In describing the stamens the union

TERMS USED IN DESCRIBING THE FLOWER 185

or cohesion is of importance. When the stamens are distinct
or separate they are said to be free, as in the Buttercup and
Rock Cress. If there are four stamens and two of them are
short and two long, they are didynamoits, as in the Deadnettle

FIG. 198. — Section FIG. 199. — Section

of flower to show of flower to show

didynamous sta- tetradynamous

mens. stamens.

FIG. 200.

Monadelphous

stamens.

and Foxglove. In the Wallflower there are six stamens ; two are
short and four long. They are said to be tetradynamous,

If the filaments are united they may be : —

Monadelphous, all in one bundle, as in the Laburnum.

Diadelphous, in two bundles, as in the Pea.

Polyadelphous, several bundles of united filaments, as in the
St. John's Wort.

Syngenesious, when the stamens are united by their anthers,
as in the Daisy and Dandelion.

The adhesion of the stamens must be
described in the following terms : —

Hypogynous, when they spring from
beneath the pistil, as in the Buttercup,
Wallflower, and Stitchwort.

Perigynous, when they are inserted on
the calyx, as in the Pea, Rose, and Apple.

Epigynous, when inserted on the top of
the ovary, as in the Fool's Parsley and
Hemlock.

Epipetalous, when united to the corolla, as in the Primrose,
Mint, and Borage.

Gynandrous, when the stamens are joined to the pistil, as in
the Spotted Orchis.

FIG. 202. — Polyadelphous
stamens.

186 BOTANY FOR BEGINNERS CHAP.

Filament.— The relative length of the filaments and pistil
must be noted. The stamens are long if .longer than the pistil,
and short if shorter than the pistil. The filament may be broad,
hairy, or petaloid. If the filament does not bear an anther the
stamen is called a staminoid.

Anther. — The anther as a rule is two-lobed, these being
joined by a rib — the connective. The anther may be united to
the filament so that it is free to swing, when it is called -versatile.
If it is joined by its base to the filament it is basifixed. When
the filament enters the back of the anther it is dorsifixed. If the
lobes of the anthers face the pistil they are introrse and when
they turn away extrorse.

Gyncecium or Pistil. — The whole collection of the carpels
of a single flower constitute the gynoecium. The cohesion of
the carpels is included in describing a flower. There are three
kinds of pistils : —

Monacarpous, when the pistil consists of a single carpel, as in
the Pea and Gorse. (Fig. 184).

Apocarpous, when there are two or more carpels and they are
separate or distinct, as in the Buttercup and Strawberry.
(Fig. 163).

Syncarpous, when there are two or more carpels and these are
united together, as in the Wallflower, Deadnettle, and Hyacinth.
(Fig. 196).

The adhesion of the pistil is superior when it is inserted above
the other parts of the flower, as in the Buttercup and Foxglove.
If the pistil is inserted below the other parts of the flower it is
said to be inferior, as in the Fool's Parsley and Daffodil.

Style. — The style may be long or short according to the
length of the stamens. It may be hairy, angular, or round. If
the style springs from the side of the ovary it is lateral, from the
top terminal, and from the base it is called gynobasic. There
will be one style to each carpel of an apocarpous pistil. In
syncarpous pistils, the styles may be separated along their whole
length or along part of their length, or united along their whole
length.

Stigma. — The apocarpous pistil will, as a rule, have one
stigma to each carpel, and in most syncarpous pistils the number
of the carpels can be obtained by noting the number of the
stigmas. Thus if there are three stigmas— the number of carpels

xiv TERMS USED IN DESCRIBING THE FLOWER 187

in the pistil will be three. The stigmas will, according to the
number present, be 2-fid, 3-fid, 4-fid, &c. They may be round,
square, feathery, or petaloid. When the style is absent the
stigmas are sessile.

Placentation. — The place where an ovule is fixed to the
ovary is known as the placenta, and the way in which they are
arranged and connected to the ovary by the placentas is called
placentation. The arrangement of the ovules in the ovary can
be determined by cutting across the ovary, and if it is small by
using a hand-lens to examine the section made. There are
several kinds of placentation, which are known as : —

Parietal Placentation, when the ovules are attached to the
walls of the ovary, as in the Poppy, Wallflower, and Pea. In
such an ovary there is generally one chamber, but in the Wall-
flower there are two. (Fig. P, 203).

Axile Placentation, when the ovary is syncarpous, and the
carpels meet in the centre and from this longitudinal axis the

P F A

FIG. 203. — P, parietal ; F, free-central ; A, axile placentation. (Diagrammatic.)

ovules grow, as in the Daffodil, Hyacinth and Tulip. The ovary
generally possesses as many cells as there are carpels ; the
ovules are attached to the axis. (Fig. A, 203).

Free-Central Placentation, when the ovary is one-chambered,
and the carpels form a swelling or column in the centre of the
ovary to which the ovules are fixed, as in the Primrose,
Stitchwort, and Chickweed. (Fig.F, 203).

Basal Placentation, when the chamber of the ovary contains
only a single ovule and this springs from the base, as in the
Buttercup.

Marginal Placentation, when in an ovary which is formed
from a single carpel the ovules are arranged along the ventral
margin, as in the Larkspur and Hellebore.

Perianth.— When the two outer whorls of the flower are
alike in colour and appearance it is called a perianth. The

1 88 BOTANY FOR BEGINNERS CHAP.

floral-leaves are then called perianth-leaves. In most
monocotyledonous plants it is usual to speak of the two
whorls — calyx and corolla — as a perianth, as in the Hyacinth,
Tulip, and Daffodil. If the leaves of the perianth are distinct,
it is polyphyllous, and if united gamophyllons. If the stamens
are united to the leaves of the perianth, they are epiphyllous.
When the perianth is coloured like petals it is said to be
petaloid.

Floral Formulae. — The number and arrangement of the
floral leaves can be clearly represented by floral formulae. In a
floral formula the whorls are represented by letters, and the
number of leaves in the whorl by corresponding figures, or ii
the numbers are large by oo . The number of rows of leaves is
represented in a whorl by + coming between the corresponding
figures. The cohesion or union of the leaves in a whorl is
indicated by ( ), the adhesion by [ ] ; and superior organs are
shown by a line below the corresponding figure, and when
inferior by a line above the figure.

If the flower is zygoinorphic or irregular the sign \ is
added. The letters used to represent the whorls are P = peri-
anth, K = calyx, C = corolla, A = andrcecium, G = gynoecium.
The following are examples of floral formulae.

Buttercup K5, C5, A oo, G oo.

Apple blossom. ..[K(s), GS, A oo,] G (5).

Foxglove f K(5), [C(s) A 4,] G (2).

Primrose K(5), [C(5), AS,] G (5).

Tulip PS + 3, A3 + 3, G(3).

Floral Diagrams. — The parts of which the flower consists
can be shown in a graphic manner by constructing a ground
plan or map of the flower. To gain an idea of the arrangement
of the whorls in a flower, cut across a flower bud so as to
separate the sepals, petals, stamens, and pistil. If the cut
surface of the flower is examined the successive floral whorls
will be seen in their proper position. The sepals will form the
outer circle and the pistil the inner one, and between these the
stamens and petals come. To construct a floral diagram make
the number of rings required with a pair of compasses, and on
the rings show the position of the floral leaves. Fig. 204 is an
example of a floral diagram.

xiv TERMS USED IN DESCRIBING THE FLOWER 189

How to describe a Flower.— In describing a flower the
following plan should be followed, taking the organs in the
order shown.

Flower. — (a) Whether complete or incomplete.

(b) Whether actinomorphic or zygomorphic.

(ff) Diameter, colour, perfume.

Calyx. — (a) Whether polysepalous or gamosepalous.

(b) Number of sepals or lobes of calyx.

(d) Shape of calyx or sepals, markings, colour, smooth or
hairy.

Corolla. — (a) Whether polypetalous or gamopetalous.

(b) Number of petals or lobes of corolla.

(t') Whether superior, hypogynous, perigynous, or epigynous.

(ft) Shape of petals or lobes of corolla.

Andrcecium.— (a) Whether free, monadelphous, diadel-
phous, or polyadelphous.

(b) Number of stamens or indefinite.

(d) Shape and length of filaments.

(e) Whether anther two-lobed, and how fixed to filament,
introrse or extrorse.

Gyncecium. — (a) Whether monocarpous, apocarpous, or
syncarpous.

(b} Number of carpels.

(d) Whether style long or short.

(<?) Whether stigmas terminal, 2-fid, 3-fid, 4-fid, &c.

(f) Whether ovary one, two, three, or more celled.

Ovules. — (a) How many ?

(b} Placentation — axile, parietal, free-central, marginal, or
basal.

Then represent the parts and arrangement of the flowers in
floral formulae and floral diagram.

190 BOTANY FOR BEGINNERS CHAP.

EXPT. 168. — Examine a flower of the Anemone and describe it,
taking its organs in the following order —

(i) Flower. — Incomplete, perfect, actinomorphic, i£ inches in
diameter, white, faintly scented.

(ii) Calyx. — Polysepalous, six in two series, inferior, sepals lanceolate
and reticulate veined.

(iii) Corolla. — Absent.

(iv) Andrcecium. — Free, indefinite, hypogynous, filaments long,
anther two-lobed, basifixed, extrorse.

(v) Gynoecium. — Apocarpous, carpels numerous, superior, styles
short, stigmas terminal.

(vi) Ovules. — One in each carpel, pendulous (suspended).

(vii) Floral formula. — K/3 + 3 Co, Aoo , G oo .

EXPT. 169.— Examine a Wallflower and describe it, taking its
organs in the following order —

(i) Flower. — Complete, actinomorphic, cruciform, i£ inches in dia-
meter, reddish-brown, sweet scented.

(ii) Calyx. — Polysepalous, four in two series, inferior, inner sepals
saccate (p. 183) lanceolate, hairy.

(iii) Corolla. — Polypetalous, four, hypogynous, petals clawed, limb
obovate, claw linear.

(iv) Androacium. — Free, six in two series, tetradynamous, hypogy-
nous, filaments thick, anthers two-lobed, dorsi-
fixed, introrse.

(v) GynoBcium.— Syncarppus, carpels two,
superior, ovary long, spuriously two-celled,
style short, stigma 2-fid.

(vi) Ovules. — Numerous, parietal placenta-
tion.

(vii) Floral formula.— K2 + 2, C4, A2 + 4,
G(«).

EXPT. 170 — Examine the flower of the
Furze (Whin or Gorse), and describe it, taking
«s organs in the following order-

(i) Flower. — Complete, zygomorphic, one
inch in diameter, papilionaceous, yellow.

(ii) Calyx. — Gamosepalous, two-lobed, inferior, green,
(iii) Corolla. — Polypetalous, five (consisting of standard, wings and
keel), perigynous.

(iv) Andrcecium. — Monadelphous, ten, perigynous, anthers two-lobed,
versatile.

(v) Gyncecium. — Monocarpous, superior, style long, stigma terminal.

(vi) Ovules. — Parietal placentation.

(vii) Floral formula.— [K( 2), GS, A(io),]Gi.

EXPT. 171,— Examine the flower of the Deadnettle and describe it,
taking its organs in the same order as before.

xiv TERMS USED IN DESCRIBING THE FLOWER 191

EXPT. 1 72. — Examine the flower of the Daffodil and describe it, taking
its organs in the same order as above.

SUMMARY.

Terms used to describe the shape and arrangement of the organs of
flowers —

The torus is the upper part of the flower stem upon which the floral
leaves are placed. Its shape varies.

A complete flower is one in which calyx, corolla, stamens and pistil
are all present.

An incomplete flower is one where one or more of the floral whorls
are absent.

A perfect flower will contain stamens and pistil.

An imperfect flower will only contain stamens or pistil.

An actinomorphic flower is one which can be divided into equal
halves in any plane.

A zygomorphic flower can only be divided into equal halves in one
plane.

The anterior parts of the flower face the bract in the axis of which
the flower stands. The posterior parts of the flower face the axis of
the inflorescences.

Shapes of flowers. — The following list gives the principal shapes
of the flowers —

Cruciform, papilionaceous, spurred, tubular, rotate, funnel-shaped,
ligulate, campanulate, personate, labiate.

Cohesion is a term used to describe union between similar parts.
Adhesion is used to describe union between dissimilar parts.

The calyx may be polysepaloiis or gamosepalous ; inferior or superior.

The corolla maybe/0/j>/<?te/0«.y or gamopetalous ; hypogynous, perigy-
nous, or epigynous.

The androecium is composed of the whole collection of stamens of a
single flower.

The cohesion of the stamens may be monadelphous, diadelphous,
polyadelphous, syngenesious.

The adhesion of the stamens may be hypogynous, perigynous, epipe-
talous, epigynous, gynandrous.

Thefl/awent may be long or short.

The anther may be versatile, basifixtd, dorsifixed.

The gynoacium is composed of the whole collection of carpels of a
single flower. There are three kinds of pistils — monocarpous, apocar-
pous, syncarpous.

The Placentation, or the arrangement of the ovules in the ovary
may be parietal, axile, free-central, basal, marginal.

The term perianth is used when the two outer whorls of a flower are
alike as in most monocotyledons.

The floral formula represents by letters, figures, lines and brackets,
the parts of a flower and their position.

192 BOTANY FOR BEGINNERS CH. xiv

The floral diagram is a graphic way of representing the flower in
ground plan.

QUESTIONS ON CHAPTER XIV.

(1) Explain the term "torus." What is its shape in the Daisy and
the Buttercup ?

(2) Define the terms fc complete " and "perfect." Mention flowers
which are perfect but incomplete, and others which are imperfect.

(3) What do you understand by hypogynous, perigynous and epigy-
nous flowers? Give two examples of each. (1898.)

(4) Describe and compare the perianth of Helleborus (Christmas
Rose), Anemone, and Ranunculus (Buttercup). (1898.)

(5) Describe the position and the general structure of the ovary in
the Buttercup, the Primrose, and the Daffodil. (1897.)

(6) Explain, with examples, the meaning of the terms — marginal,
axile, and parietal placentation. (1894.)

(7) Explain, with examples, the meaning of the following terms
applied to stamens — diadelphous, tetradynamous, didynamous, syn-
genesious, epipetalous. (1890.)

(8) Describe and compare the flowers of the Narcissus and the
Hyacinth. (1893.)

(9) Describe, with examples, the papilionaceous, the labiate, and the
personate types of corolla. (1891.)

(10) What is meant by " zygomorphic symmetry " ? Give examples.

CHAPTER XV

THE DEVELOPMENT AND MORPHOLOGY OF THE FLOWER

The Development of the Flower.— The young flower
buds appear on the stem as rounded outgrowths, and if a series
of these is examined by cutting transverse sections through
them, the order of development of the floral whorls can be ascer-
tained. If a series of flower buds of different ages is examined
from the inflorescence of the Wallflower, the very young bud
will show the calyx just appearing. The first sepal to appear is
the anterior one, then the two lateral ones are developed, and
last of all \\\t posterior one. In a little older bud the corolla will
be found as four little projections just within the sepals, and
alternating with them. All four petals appear at once. In
buds a little older still the stamens will be seen inside the
corolla. The order of the appearance of the stamens is as
follows : —

i. — The anterior pair of long stamens appear first.

2. — The lateral pair of short stamens next.

3. — The posterior pair of long stamens last.

The pistil is the last floral organ to appear ; the two carpels
arise together, and can be seen as small projections in the centre
of the bud.

The order of the development of the floral whorls can be far
better made out in those flowers which are closely associated in
large numbers in inflorescences, like the capitulum or head,
(p. 1 68). Thus, in the young inflorescence of the Daisy or the
Sunflower, nearly all the stages of development can be seen
in a single section. If a young capitulum of the Daisy is
examined with a hand-lens, the youngest flowers can be seen

194 BOTANY FOR BEGINNERS CHAP.

near the centre, and the oldest towards the edge. From the
centre to the edge all stages in the development of the floral
organs can be made out. If a section is .cut through a young
capitulum, and the section treated with potash solution for a
short time, and then mounted in glycerine and examined with
a high power — the central flowers will show the corolla appear-
ing as five small lobes. In an older flower, just within the
corolla, five projections will be seen — these are the stamens.
In a still older flower the centre of the stamens will be filled in
with two carpels, which form the pistil.

Thus, in the Daisy the corolla appears first, then the stamens,
and last of all the pistil. In the Sunflower the corolla and
stamens appear as in the Daisy, then the calyx, and last of
all the pistil. In the large majority of plants the appearance
of the floral whorls is the same as in the Wallflower, but as we
have seen there are exceptions.

EXPT. 173. — From the raceme of the Wallflower cut off the young
buds from the apex and lay them in regular order, placing the oldest
at one end and the youngest at the other end. With a sharp knife or
razor cut the buds into halves transversely, beginning with the oldest.
Examine with a hand-lens. Note —

(i) The oldest bud shows the petals, stamens and pistil coiled up
inside the calyx, the parts being very distinct.

(ii) The anthers show small openings. These are called the pollen
sacs.

(iii) The pistil is two-celled, and within it the ovules can be seen.

(iv) From the oldest onwards the parts are less distinct.

(v) In the younger buds the pistil is the least distinct, then stamens
and corolla ; the calyx is the best developed of all the parts.

(vi) This shows that the calyx is developed first and the pistil last.

EXPT. 174. — Collect a number of inflorescences of the Daisy or
Dandelion, and examine them with a hand-lens. Note —

(i) The shape of the inflorescence. It forms a cone which is irregular
in outline.

(ii) The younger inflorescences show the central flowers just ap-
pearing.

(iii) The largest and oldest flowers are near the edge of the inflor-
escence, and the younger and smaller flowers in the centre.

(iv) This shows that the growing point cuts off floral leaves from the
outer part of the torus first and from near the apex last of all.

The Structure and Functions of the Sepals.— The
green sepals resemble the foliage leaves in structure and ap-
pearance. They are covered with an epidermis, which contains

xv THE DEVELOPMENT OF THE FLOWER 195

stomata, and between the upper and lower epidermis comes the
mesophyll, which is penetrated and strengthened with vascular
strands.

The Texture of the Sepals. — The texture of sepals varies con-
siderably. They may be delicate, firm, membranous, or scaly.
The duration of the sepals will depend upon their texture. They
may fall off when the flower opens, when they are said to be
caducous; if they last until the seeds begin to ripen and then
fall off, they are deciduous ; and when they remain until the seeds
are ripe, they are persistent. The surface of the sepals is fre-
quently provided with hairs for protection.

Functions of the Sepals. — When the sepals are green they
perform the same functions as foliage leaves. They also serve
to protect the other floral leaves from injury. If they are petaloid
they may serve to attract insects, as in the Anemone and
Lilies.

The Structure and Functions of the Petals. — The
petals and petaloid sepals are covered with a delicate epidermis.
Within the epidermis come one or more layers of spongy paren-
chyma ; this is traversed with a number of delicate vascular
strands, which, as in foliage leaves, gives it a veined appearance.

The Texture of the Petals. — The texture of the petals is
usually delicate. They are deciduous, z>., they fall off as the
seeds ripen. The surface of the corolla may be smooth or
glabrous (p. 29), or present certain hair structures or hair-like
outgrowths.

The Colour of Petals and Sepals. — When the sepals and (less
often) the petals are green, the colour is due to chlorophyll.
The petals are, however, as a rule coloured, the colour being
due either to coloured sap or to chromoplasts (p. 84). In a
few cases the colouring is due to both.

The Functions of the Petals. — The colour, markings, shape,
and perfume of the corolla are all designed to attract insects,
so as to ensure the distribution of the pollen (p. 198). The
petals also protect the essential organs (stamens and pistil) of
the flower from injury. Petals may be modified to form nectaries
or glands for the preparation of honey. Petals thus have a two-
fold function, attractive aud protective.

EXPT. 175. — From a flower of the Geranium strip off a petal, and with
a sharp knife pull away the surface tissue. Mount the petal in water

0 2

196 BOTANY FOR BEGINNERS CHAP.

with the torn surface below, and examine under a low power.
Note—

(i) The conical-shaped outline of the cells.

(ii) The cells contain coloured cell-sap. There are no chromoplasts
present.

EXPT. 176. — Cut transverse sections through a sepal of the Wall-
flower, mount the thinrtest in water, and examine with the high power.
Note —

(i) The epidermis on both the upper and lower surfaces.

(ii) The mesophyll between the upper and lower epidermis, it
contains vascular bundles.

EXPT. 177. — Harden a few petals of the Wallflower in alcohol, and
cut transverse sections. Select the thinnest and mount in glycerine.
Examine under the low power. Note —

(i) The short hairs growing out from the epidermal cells. These give
the characteristic appearance to the petals because they reflect the
light.

(ii) The vascular bundles are slender, but consist of xyleni and
phloem.

(iii) The mesophyll is built up of parenchyma cells.

(iv) The epidermis contains no stomata.

EXPT. 178. — Examine with the hand-lens the base of a single petal
of the Buttercup. Note —

(i) The pocket-like nectary which secretes honey.

Place it in alcohol for a short time, and mount in water. Examine
it with a low power and reflected light. Note —

(ii) The vascular bundles, which give to the petal a veined appearance.

(iii) The epidermis, which consists of small but regularly arranged
cells.

(iv) The colouring matter has nearly all disappeared.

The Essential Floral Organs.— The androecium and
gyncecium form the essential floral organs. They are called the
essential organs of the flower, because without them no seeds
can be produced. The calyx and corolla are not essential for
the formation of seeds, since many plants which have only
stamens and pistil produce seeds. The calyx and corolla do,
however, perform useful work in protecting the essential organs
from loss of heat as well as from dew and rain ; they also by
their colour, perfume, and shape attract insects to the flower.

The Structure of the Androacium.— The andrcecium 01
a flower consists of modified leaves, which bear very little re-
semblance to foliage leaves. Each stamen is, as a rule, filiform
in shape, and consists of a filament or stalk bearing an anther at
the apex. They have no vegetative function to perform, but are

XV THE DEVELOPMENT OF THE FLOWER 197

modified for special work— that of producing pollen. The fila-
ment represents the petiole of the foliage-leaf, and it is traversed
by one or more . vascular bundles, which is surrounded with
endodermis. The vascular cylinder is surrounded by paren-
chyma cells, and these again by an epidermis. As a rule there
are no stomata in the epidermis of the filament.

The anther represents the blade of the foliage leaf folded to
form four cavities — \hzpollen sacs. Up the centre of the anther,
and dividing it into two lobes is a midrib — the connective. In
the centre of the connective runs a vascular bundle, continuous
with the bundles of the filament, and bringing nutritive matter
to the anther. The walls
of the mature anther, as
seen in a transverse sec-
tion, consist of the follow-
ing parts ;—

I. — The epidermis, the
outer walls of which have
a well-developed cuticle,
and may contain a few
stomata.

T7, -fih~* /,,, FIG. 205.— Transverse section of anther of Wall-

2.— The fibrous layer flower;> ^ wall of pollen sacs . vbt vascuiar
consisting of several bundle,
layers of cells, which

present a stratified appearance, due to the thickening of the
walls.

3. — The tape turn layer, sometimes represented by nearly dis-
organised cells, for it is used for the nutrition of the pollen
grains. The young anther contains four pollen sacs, but the
mature one only two ; this is owing to the two pollen sacs in
each lobe of the anther uniting just before it becomes ripe.
The pollen sacs contain pollen. Each pollen grain is a male
reproductive cell.

The Development of the Stamens.— The first part of
the stamen to appear is the anther, and this is formed by the
division of a number of cells just below the epidermis. These
cells -are, because of their position, called hypodermal cells ; they
form what is called the archesporium or meristem layer from
which the anther and pollen grains are formed. The cells of the
archesporium divide at four points in the young anther, which

198 BOTANY FOR BEGINNERS CHAP.

correspond to the four pollen sacs. The cells formed by their
division give rise to

i. — The cells of the fibrous layer.
2. — The cells of the tapetum layer.

3. — The pollen mother cells, formed from the inner cells.
4.— The epidermis of the anther, formed from the cells above
the hypodermic layer.

The filament is the last portion of the stamen to be produced ;
as a rule, it is not fully developed until just before the pollen is
ripe.

The Development of Pollen.— Dicotyledons.— The pol-
len mother-cells are large, thin-walled, filled with protoplasm and
contain a large nucleus. They are more or less rounded in out-
line and a very large number of them occur in each pollen sac.

FIG. 206. — Diagram illustrating the development of pollen in a dicotyledonous anther.

Each mother-cell divides into four pollen grains in the following
manner. The nucleus divides (p, 89) into two, and each half
again divides into two, so that there are four nuclei in the
mother-cell. The protoplasm becomes rounded off so as to
form separate masses round each nucleus. (Fig. 206). A new
cell wall is produced round each nucleus from the protoplasm,
thus separating the daughter-cells, as they are called. Each
cell after ripening forms a pollen grain. The pollen grains are
set at liberty by the breaking down of the wall of the mother-
cell. This method of formation of pollen is the common one for
all dicotyledonous plants.

Monocotyledons.— -In monocotyledonous plants the formation
of pollen differs from the method just described. The nucleus
of the mother-cell divides into two parts, and between -these
parts a cell wall is formed which extends right across the cell.
Each nucleus again divides and new cell walls are formed be-
tween them. Thus, out of the mother-cell four daughter-cells

THE DEVELOPMENT OF THE FLOWER

199

are formed. The principal difference, then, is the division by a
wall of the cell into two after the division of the nucleus. (Fig.
207). The pollen grains of dicotyledonous plants are formed
by free cell formation, but in monocotyledonous plants by a
method which comes between this and vegetative division,
(p. 89).

The Structure of a Pollen Grain.— The pollen grain is
at first surrounded by a very thin cell-wall which with age in-
creases in thickness. The outer layer becomes cuticularised
and forms the extine', the inner layer consists of cellulose and

FIG. 207. — Diagram illustrating the deve- FIG. 208. — Pollen grain. E, extine ;
lopment of pollen in a monocotyle- I, inline ; N, vegetable nucleus ;

donous anther. G, generative nucleus. (Dia-

grammatic.)

forms the intine. The shape of the grain varies in different
plants. The extine, too, may be raised into knobs, spines, and
ridges or be perfectly smooth. Most pollen grains have thin
places in their extine and out of one of these places the intine
grows to form the polle?i tube.

The interior of the grain is filled with granular protoplasm, in
which two nuclei may with great difficulty be made out. The
smaller nucleus is the generative one, and the larger one the
vegetative nucleus. When the pollen grain is placed under suit-
able conditions (p. 152) germination takes place, and the intine
breaks through the extine to form a long tube called the pollen
tube, which is of service in carrying the generative nucleus to the
ovule.

EXPT. 179. — Cut a transverse section from the filament of any well-
developed stamen. Mount in water and examine, first with a low, then
with a high power. Note —

(i) The outside epidermal layer.

(ii) A few rows of parenchyma within the epidermis which represent
the cortex of the petiole.

(iii) One or more vascular bundles in the centre of the section ; these
are continuous with the bundles of the stem, and bring nutritive
materials to the anther and pollen grains.

200 BOTANY FOR BEGINNERS CHAP.

EXPT. 1 80. — Cut transverse sections of the young flower bud of the
Wallflower. Mount the thinnest in water and examine with a low
power. Neglecting the other parts of the flower, look for an anther.
Note—

(i) A single layer of cells, the epidermis, the outer walls of which
possess a well-developed cuticle.

(ii) The fibrous layer, which is several layers of cells in thickness and
appears striated.

(iii) The tapetum layer. This is represented by a layer of cells in all
stages of disorganisation.

(iv) The four pollen sacs.

(v) The pollen grains. Some are in the pollen sacs, others in the
water.

EXPT. 181. — Transverse sections of a ripe anther of the Wallflower
should be made for comparison. To do this it is necessary to harden
in alcohol for a few days. Select the thinnest and mount in glycerine.
Note—

(i) The layers are the same, but better developed.

(ii) There are only two pollen sacs.

(iii) The pollen grains are ripe.

Examine a pollen grain with a high power. Note —

(iv) The thin places in the wall through which the intine grows to
form the pollen tube.

(v) The nuclei, the largest^ is the vegetative one, and the two smaller
ones are the generative ones. These will be seen with difficulty.

EXPT. 182. — Mount in water and examine the pollen grains of the
following flowers as they appear — Rock Cress, Sunflower, Hyacinth,
Apple, Deadnettle, &c. Note—

(i) Their shape and external markings.

(ii) The thin places in their walls.

(iii) Their comparative sizes.

EXPT. 183. — Cut a piece of cardboard the size of a microscopic slip,
and out of the centre remove a circular piece the size of a cover-glass.
Fix the cardboard to the glass slip with a thin layer of Canada balsam
and dry ; place a drop of a six per cent, solution of sugar in the cell
you have formed in the cardboard. Mount a few pollen grains from
the Wallflower in the sugar solution, and cover with a cover-glass.
Examine with the high power of microscope. Note —

(i) The thin places in the wall of the grains.

Damp the cardboard and put in a dark warm place for a few hours.
Note —

(ii) Many of the grains have sent out pollen tubes filled with granular
protoplasm.

(iii) One or more nuclei may be detected in the pollen tube.

How the Pollen is liberated from the Anther.— When
the anther is ripe, the pollen sacs open so as to set the pollen
grains at liberty, The anther lobes may open by one split

xv THE DEVELOPMENT OF THE FLOWER 201

marking the line of junction between two pollen sacs, when the
opening is called longitudinal dehiscence. In other cases the
anther opens by small pores, as in the Heath and Potato, when
the dehiscence is porous. In the Barberry, the anthers open by
small doors or valves when the dehiscence is valvular.

The Structure of the Gyncscium.— The gyncecium con-
sists of modified foliage leaves which depart even more widely
than the stamens from the ordinary foliage leaf type. The
structure of the carpels, as these modified leaves are called, can
be made out if transverse sections are cut and examined by the
microscope. Each carpel is found to consist of the following
parts : —

I. — Lower and upper epidermis.

2. — Several layers of mesophyll.

3. — A number of vascular strands which penetrate the
mesophyll, and bring nutritive material to the carpel and its
ovules.

The gyncecium may consist of a single carpel, as in the Pea ;
or of several carpels, as in the Poppy and Lily. In every case
the carpel or carpels are united so as to form a cavity or cavities
— the ovary. In the ovary the ovules are developed, and they
receive the materials necessary for their further growth from the
ovary.

The Structure of an Ovule.— An ovule consists of the
following parts : —

i. — The funiculus or stalk by which it is attached to the
placenta or swelling on the wall of the ovary (p. 10).

2. — The integuments or coverings of the ovule, which are
several layers of cells in thickness. There is a small opening
through the integuments, the micropyle. (p. 10).

3. — The nucelluS) an oval mass of tissue within the integu-
ments.

4. — The embryo-sac embedded in the nucellus.

The Embryo-Sac.— The embryo-sac is a large oval cell
which contains : — (i) The embryo-sac nucleus placed in the
centre of the sac. (ii) The egg-apparatus, which consists of
three cells at the micropyle end of the embryo-sac. One of
these receives the name of the ovum or oosphere and is the cell
from which the embryo is developed. The other two form the
Synergidce, and direct the pollen tube to the oosphere. (iii) The

202 BOTANY FOR BEGINNERS CHAP.

antipodal cells, which consist of three cells which are placed at
the posterior end of the embryo sac. In many cases these
disappear before the ovule is ready for fertilisation, (iv) The
granular protoplasm, in which the above structures are em-
bedded, (v) The vacuole, which is filled with cell-sap.

The funiculus unites the ovule to the wall of the ovary and con-
tains a vascular strand which carries the nutritive materials neces-
sary for the development of the ovule and embryo or young plant.
The integuments protect the nucellus and embryo-sac from injury.
In a few plants the integuments may not be developed. The
most important part of the ovule is the embryo-sac with its
contents.

EXPT. 184. — Cut transverse sections through the open flower of the
Marsh Marigold. Wash the section from the razor with water into a
watch-glass. Mount a section containing ovules in dilute glycerine.
Examine under a low power. Note —

(i) The ovules connected to the carpel by short stalks — the funicles.

(ii) The embryo-sac, which is very large.

Examine the embryo-sac under a high power. Note —

(iii) The egg apparatus, which consists of synergidoe and oosphere.

(iv) The antipodal cells at the far end of the embryo-sac from the
micropyle,

(v) The embryo-sac nucleus.

~~ The Development of the Gyncecium :— The gyncecium
is the last part of the flower to appear, and it always occupies
the apex of the floral axis. The carpels may be separate as they
are developed and afterwards unite, or they may remain separate
(as in an apocarpous gyncecium). (p. 186). The zone of tissue
just below the carpels begins to develop and carry up the carpels
with it. The union of the carpel or carpels forms the ovary.
Ridges appear on the wall of the ovary. These are the placentas
from which the ovules will be developed.

The Development of the Ovules.— The ovules are formed
as outgrowths of the placentas. Each ovule at first consists of
two layers of cells belonging to the epidermis of the wall of the
ovary, and to a deeper layer just below it. One cell is larger
than its neighbours and from this the embryo-sac and its contents
are formed. The integuments and the nucellus are formed from
the cells at the base of the projection. The funicle is also formed
from the cells at the base of the ovule and fixes it to the
placenta.

THE DEVELOPMENT OF THE FLOWER

203

The large cell which we may call the embryo-sac continues to
grow, and its nucleus, — that is, it must be remembered the prim-
ary embryo-sac nucleus — divides and the two daughter
nuclei move to the ends of the embryo-sac. They both divide
again. There are thus two at each end of the sac. These again
divide, so that there are eight nuclei in the embryo-sac, four near
each end. The protoplasm now forms around three of the nuclei
at each end. The three at the end nearest the micropyle form
the egg-apparatus, and those at the opposite end the antipodal
cells. One nucleus from each end passes towards the middle of
the sac. These unite and form the secondary embryo-sac
nucleus.

Kinds of Ovules. — There are three common types of ovules,
and the names which they receive depend upon the relative posi-
tions of the funiculus and body of ovule. These are explained
by the figures given. They are as follows : —

i. — The ovule is Orthotropous (atropous) when the funiculus
and the axis of the ovule forms a continuous line (Fig. 209, A).

Fig. 209. — Diagrams of Ovules. A, orthotropous ; B, anatropous ; C, campylotropous.
(After Strasburger.)

The nucellus is then straight, and the micropyle is at the greatest
possible distance from the funiculus.

2. — The ovule is Anatropous when the funiculus curves sharply,
so that it lies side by side with the body of the ovule. (Fig. 209, B).

3- — The ovule is Campylotropous when the ovule is itself
curved so that the micropyle and the chalaza, or basal portion of
the ovule, do not lie in the same straight line. (Fig. 209, C).

204 BOTANY FOR BEGINNERS CHAP.

SUMMARY.

The floral whorls are developed in the following order —

The calyx. — The anterior sepal appears first, next the lateral, and
finally the posterior sepal.

The corolla. — All the petals appear together.

The stamens. — The anterior pair appear first, next the lateral pair,
and finally the posterior pair.

The pistil. — The carpels appear together.

The sepals resemble foliage leaves in structure and appearance. They
protect the essential organs from injury, and if petaloid may attract
insects.

The petals differ from foliage leaves in colour and texture. Their
principal function is to protect the essential organs, and by their shape,
colour, and perfume to attract insects.

The essential floral organs consist of andrcecium and gyncecium.
These are essential for the production of seeds. The andrcecium pro-
duces pollen, and the gyncecium ovules.

The structure of the androecium. — It consists of modified leaves,
bearing very little resemblance, however, to foliage leaves. Its
function is to produce pollen and liberate it. The filament of an
anther represents the petiole of a foliage leaf and the anther lobes the
blade.

The anther consists of the following layers of cells —

(a) The epidermis ; (b} the fibrous layer ; (c) the vascular bundle ;
(d) the tapetum layer, which generally disappears during the development
of the pollen ; (e) the pollen sacs.

The development of pollen takes place in the pollen sacs. The
mother pollen cells divide up to form four daughter cells — the pollen
grains.

This division takes place in the following way —

(a) The nucleus divides into two ; (b) the two nuclei divide into
two each ; (c] the protoplasm becomes rounded off to form four cells
round the protoplasm ; (d) the mother cell-wall becomes disorganised
and the daughter cells are set at liberty as pollen grains.

The pollen grain consists of a cell-wall, the outer part of which is
cuticularised to form the extine ; the inner, or intine, is very delicate
and consists of cellulose. The interior of the grain contains —

(a) A large nucleus — the vegetative one ; (b) a small nucleus — the
generative one. These are embedded in the protoplasm.

The anther may liberate its pollen — (a) by longitudinal slits, when the
dehiscence is longitudinal ; (b} by pores, when the dehiscence is porous ;
(c) by valves, when the dehiscence is valvular.

The gyncecium is built up of carpels. Each carpel is a modified
leaf, and it consists of —

(a) The epidermis ; (b) mesophyll ; (c) vascular bundles. The
carpel may contain ovules.

The parts present in an ovule are —

(a) The funiculus or stalk ; (b) the integuments or coverings of the
ovules ; (<•) the nucellus in which (d] embryo-sac is embedded.

xv THE DEVELOPMENT OF THE FLOWER 205

In the embryo-sac the parts present are —

(a) Egg apparatus— synergidae, oosphere ; (b} antipodal cells ; (c) em-
bryo-sac nucleus ; (d) protoplasm.

The first part of the gynoecium to be developed is the stigma. This
is carried up by the growth of the tissue beneath. The ovary is the last
part to appear. The union of the carpel or carpels forms the ovary.

The kinds of ovules are as follows —

(i) The orthotropous ; (ii) the anatropous ; (hi) the campylotropous.

QUESTIONS ON CHAPTER XV.

(1) State what you know about the development of (a) the calyx,
(d) the corolla, (c) the stamens, and (d) the pistil, in any flower of your
own selection.

(2) What is the structure of (a) the calyx, and (b) the corolla of any
flower ? Of what use are they to the plant ?

(3) Describe the structure of an anther and of a pollen grain. (1890.)

(4) What is pollen? Give an account of its development and its
function. (1893.)

(5) How are the pollen grains set at liberty? Give examples.

(6) Describe the contents of the embryo sac at the time when fertil-
isation is about to take place. (1891.)

(7) Give a description of the successive stages in the development of
the embryo-sac in any plant. (1894.)

(8) Explain the use of the stigma, and describe the structure of the
stigma of any flower you may select.

(9) Describe, giving an example of each, the anatropous, the ortho-
tropous, and the campylotropous ovule. (1898.)

(10) What is a pollen tube? How is it produced, and what is its
use?

(n) Of what parts does an ovule consist? Where are ovules found,
and how are they held in position ?

( 1 2) Explain with diagrams the following terms — anatropous, tapetum,
synergiclae, antipodal cells.

CHAPTER XVI

POLLINATION AND FERTILISATION

Flowering Plants.— There is one feature in which all
flowering plants differ from non-flowering plants — that is, the
production of seeds. They are often spoken of as seed plants
in contradistinction to seedless plants. If certain conditions
are fulfilled, the ovules become changed into seeds. There is
no other way in which seeds can be produced, except by
changes in the ovules which convert them into seeds. The
ovules of to-day become the seeds of to-morrow, and the seeds
of to-morrow form the plants of the future.

The conditions which are necessary for the conversion of an
ovule into a seed are as follows : —

(1) The pollen gram formed in the anther must find its way
on to the stigma of the pistil. This transference of the pollen
from the andrcecium to the gyncecium is called pollination.

(2) The pollen grain must germinate and form a pollen tube,
which must grow down the style and enter the micropyle of the
ovule. The generative nucleus of the pollen grain must be set
at liberty and unite with the oosphere in the embryo-sac. The
union of the generative nucleus of the pollen grain with the
oosphere is called fertilisation.

(3) The oosphere after fertilisation is called an oospore or
egg-spore, an(i must develop into an embryo or young plant
(P- ii).

(4) Food materials must be removed from the leaves of the
plant into the embryo-sac, there to be used up by the developing
embryo during its early growth, or to be stored until the
germination of the seed takes place,

CH. xvi POLLINATION AND FERTILISATION 207

Pollination. — Pollination may take place in two different
ways.

(1) Cross- Pollination. — When the pollen of a flower is dis-
tributed to the pistil of another flower it is said to be cross-
pollinated.

(2) Self-Pollination.— When the pollen of a flower is dis-
tributed to the pistil of the same flower it is said to be self-
pollinated.

Cross-Pollination. — It has been proved with many plants
that cross-pollination produces a better crop of seeds ; and that
the plants produced from these seeds are stronger and better
able to survive in the struggle for existence. It was pointed
out by the late Charles Darwin * that cross-pollinated flowers
produce offspring which possess (a) greater strength ; (b} the
habit of earlier flowering ; (c) greater diversity of colour, than
the self-pollinated flowers. Cross-pollination can take place in
two ways : —

(1) By the pollen being carried from the anther of one flower
to the pistil of another flower by insects. Those plants which
possess flowers which are pollinated by insects are called
cntomophilous or " insect-loving " plants.

(2) By the pollen being carried from the anther of one flower
to the pistil of another flower by the ivind. Those plants
which possess flowers which are pollinated by the wind are
called anemophilous, or " wind-loving " plants.

Why Insects visit Flowers. — Insects are attracted to
flowers by their shape, colour, and perfume. Many flowers also
produce honey which the insects use for food. Organs which
produce honey are called nectaries or honey-glands (p. 195).
These nectaries occupy different positions in different plants.
Thus, in the flowers of the Wallflower there are two nectaries,
which occur at the base of the short stamens, and the sugar
solution or honey which they produce is stored up in the
saccated lateral sepals. In the Christmas Rose, the modified
petals, which are tubular in shape, bear nectaries. The nectary
in the spotted orchid is in the twisted spur, and it is necessary
for the bee to put its tongue or proboscis down this spur in order

1 The Cross and Self -Fertilisation in Plants.

208 BOTANY FOR BEGINNERS CHAP.

to reach the honey. In fact any part of the flower may be
modified for the secretion and reception of honey.

Insects cannot live on honey alone for it contains no nitrogen,
and nitrogen is just as necessary for the life of animals as for
plants. Many coloured flowers do not produce honey, but
plenty of pollen, the pollen being collected by insects for their
food. The pollen, since there is a fair amount of protoplasm in
it, contains nitrogen. Bees, for instance, possess small brushes,
on the end of their appendages or limbs, which are used to
brush the pollen from the surface of the body. The pollen is
then moistened and rolled up into little balls, which are stored
in a little sac in one of the limbs until the hive is reached. The
Broom is a plant which does not produce honey, but which is
visited by crowds of bees for the sake of its pollen, which it
produces in large quantities. Insects are of service to plants
because they distribute the pollen from flower to flower, and the
plants in return supply them with honey and pollen for food.

Contrivances to Prevent S elf-Pollination.— The im-
portance of cross-pollination to many plants has produced many
contrivances to prevent self-pollination, and to enable the far
more successful cross-pollination to take place. The principal
arrangements by which flowers facilitate cross-pollination must
now be described.

(1) The stamens and carpels may be produced in different
flowers. In such a case it is necessary for the pollen to be
carried from flower to flower. Such flowers are said to be
diclinous. The stamen-bearing flowers and the carpel-bearing
flowers may be produced on the same plant, as in the Birch,
Hazel, and Pine, when it is said to be monoecious. The stamen-
bearing flowers may be produced on one individual, and the
carpel-bearing flowers on another individual plant, as in the
Dog's Mercury and Willow, when the plant is said to be
dioecious.

(2) Both stamens and carpels are present in most of the
common flowers, and the flower is said to be monoclinic. In
such a flower self-pollination may be prevented by the stamens
and carpels ripening at different times. If the stamens ripen
and distribute their pollen before the carpels of the flower
bearing them are ready for pollination, the flower is said to be
protandrous, as in the Dog Daisy, Stitchwort, and Harebell

POLLINATION AND FERTILISATION 209

When the carpels ripen and are pollinated before the stamens
of the same plant are ready to distribute their pollen, the
flower is said to be protogynous, as in the Plantain (Fig. 212).

(3) The arrangement of the stamens and stigma may be dif-
ferent in the same flower, as in the Cowslip and Primrose. The
style of one flower may be long and the stamens short, and in
another flower the stamens long and the style short. Thus, th&
pollen of a short-styled flower would reach the stigma of a
long-styled flower, and the pollen of a long-styled one would
reach the stigma of a short-styled flower (p. 210).

(4) The pollen of a flower may have no effect on the ovules
of the same flower, as in most Orchids.

Cross-Pollination by Insects.— We have seen that
insects visit flowers in search of honey and pollen. They also
aid in the distribution of pollen from flower to flower.
Most entomophilous plants produce flowers which have the
following characters : —

i. — They are brightly coloured, sweet-scented, and very
prominent.

2. — They produce honey and pollen, or pollen only, the insects
visiting them to collect food.

3. — They produce pollen-grains which are generally sticky
so that they will adhere to the body of insects and to the stigma.

4. — They produce stigmas which are generally sticky, and are
placed so that insects must brush them as they pass into the
flower in search of honey or pollen.

We will now consider how cross-pollination is produced by
insects by taking a few typical examples.

i.— Dimorphic Plants.— If the flowers from a few Cowslip
plants are examined the stamens in one will be found at the top
of the corolla tube, and the stigma half-way down the tube. In
another specimen the stigma will be at the top of the tube,
and the stamens half-way down the tube. The first flower has
short style and long stamens, and the second, a long style and
short stamens. The Cowslip, and all other plants the individual
flowers of which vary in the lengths of their styles and stamens,
are said to be heterostyled. If there are only two lengths of
styles, the plants are called dimorphic. (See Primulacae,
p. 268).

2io BOTANY FOR BEGINNERS CHAP.

EXPT. 185. — Collect a few flowers of the Cowslip or Primrose and
examine them. Select one where the stigma appears at the top of the
corolla tube, and another where the stamens occupy a similar position.
Open each corolla by inserting a knife at the bottom of the tube, and
making a vertical cut so as to lay them open. On the long-styled^ one,
note —

(i) The stamens are half way down the tube, and the style at the top
of the corolla tube.

On the short-styled one, note —

(ii) The style is half way down, and the stamens at the top of the
corolla tube.

Place the flowers side by side, and measure the relative lengths of
styles and stamens, note —

(iii) The long style is on the same level as the stamens in the short -
styled flower, and the stamens in the long-styled flower are on the same
level as the short style.

(iv) The honey which is at the base of the corolla tube.

In the two forms of the Cowslip, the size of the pollen grains are
different, and the structure of the top of the stigma varies. The differ-
ence of the two forms is seen below in a tabular form.

Long-Styled. Short-Styled.

Flowering. . . A little later Earlier

Stamens ... Short Long

Pollen Grains smaller Grains larger

Style Long Short

Stigma Globular hairs long Flattened hairs short.

The larger pollen grains of the short-styled flowers are
necessary because they have to pollinate the long-styled flowers,
and a longer pollen tube will be necessary to reach the ovule in
the ovary. Thus they contain materials for the production of a
longer pollen tube. The longer hairs on the stigma of the long-
styled form are to prevent the pollen grains from being blown
away by the wind.

The Work of the Insect. — When the insect visits the Cowslip
for honey, its proboscis or tongue is passed down the tube of the
corolla to reach the nectary at its base. If the flower is a long-
styled one, the tongue is dusted with pollen at a certain point,
and if the next flower visited is a short-styled one, the pollen is
placed on the top of the flattened stigma. In the short-styled
flower the tongue of the insect is dusted with pollen higher up —
this is deposited on the stigma of the long-styled flower. Thus
the proboscis of the insect is the medium for the distribution of
the pollen, and so produces cross-pollination.

XVI

POLLINATION AND FERTILISATION

This description will do for most dimorphic plants, among
which the Primrose, Lungwort, and Common Flax are
examples.

2.— Trimorphic Plants.— If a few flowers of the Purple

Loosestrife are collected from different plants and examined

'they will be found to be heterostyled, and in addition trimorphic,

i.e., with styles of three different lengths. The arrangement of

the styles and stigmas is seen from the following description : —

(A) Flowers, where the stamens are in two sets — a short set
and a long set — the

top of the style
(stigma) coming
between the two.

(B) Flowers,
where the stamens
are in two sets —
one set of the same
length as the short
stamens in A, the
other of the same
length as the style
in A. The style is
longer than the two
sets of stamens.

(C) Flowers, where the stamens are in two sets — one set on
the same level as in the long style in B, and the other set level
with the style in A. The style is shorter than the two sets of
stamens.

Thus, there are short-styles, medium-styles, and long- styles.
There are short-stamens, medium stamens, and long-stamens.
(Fig. 210).

EXPT. 186. — Collect flowers of the Purple Loosestrife from different
plants. They can be found in damp places in July and August.
Examine them. Note —

(i) The long tubular calyx, near the top of which the distinct,
crumpled, purple petals are inserted.

(ii) The stamens inserted in the calyx tube, but much lower down
than the petals.

(iii) The syncarpous (p. 186) pistil of two carpels, which possesses one
style and one stigma.

Now dissect with care a number of the flowers, and arrange them
into three series according to the comparative lengths of the stamens

P 2

FIG. 210 — Diagram of trimorphic forms of the
Loosestrife.

212 BOTANY FOR BEGINNERS CHAP.

and stigmas. Separate the petals from the calyx, and open the tube of
the calyx so as to show the position of the stamens and stigma.
Note—

(iv) Those flowers where the stigma comes between the two sets of
stamens. The style is of mid-length, the stamens are long and short.

(v) Those flowers where the stigma is long — the two sets of stamens
coming below it. The stigma is long, the stamens are of mid-length '
and short-length.

(vi) Those flowers, where the stigma is short — the two sets of stamens
are inserted above it. The stigma is short — the stamens are of mid-
length and long-length.

Now mount pollen from the different sets of stamens in water.
Examine with low power. Measure the size of each, and note which
are the largest and which the smallest.

(vii) The pollen grains from the long stamens of the short-styled form
are the largest. Why ?

(viii) The pollen grains from the shortest stamens of mid-styled form
are the smallest. Why ?

The Work of the Insect— -In a plant of this description the
pollen is distributed by insects. From the examination of
« the flowers it is seen at once that the insect

carries pollen from the short stamens to the
short stigma ; from the mid-stamens to the
mid-stigma ; from the long-stamens to the
long-stigma.

3. — British Orchids. — The most highly
developed of all entomophilous plants are the
orchids. They are noted for their peculiar
FIG 211 —Floral Dia- shapes and the beauty of their flowers. Re-
gram of Orchid. prcsentatives of this order of plants are found
in nearly all parts of the world, and men are
constantly engaged in tropical and sub-tropical climates in
looking for new specimens. One of the common British
representatives is the Spotted Orchis, which makes gay many
a lane and bog in the North, and decorates the Sussex Downs
and most sea-cliffs in the South.

EXPT. 187. — Dig up a single plant of the Spotted Orchis when in
flower, and examine it. Note —

(i) From the tuberous root rise several smooth, parallel-veined,
spotted leaves.

(ii) From the centre of the leaves springs the peduncle, which bears
a nearly pyramidal head of many purple flowers.

(iii) From the peduncle carefully remove one of the flowers and hold
it in the same position as that assumed by it when on the stem. A

POLLINATION AND FERTILISATION

twisted stalk to all appearance connects it to the peduncle. Cut across
this supposed stalk — it is full of ovules — in fact, it is the ovary.

Now examine the flower, it is zygomorphic (p. 179). Note —

(iv) The perianth is gamophyllous (p. 188), six-lobed, and superior
(p. 183). The largest leaf of the perianth is called the labellum, and is
roughly divided into three lobes ; it forms a spur below, which contains
a nectar}'.

(v) The single stamen, the anther of which is united with the pistil,
and is consequently said to be gynandrous. The stamen terminates
below in a little knob called the rostellum or little beak, and this stands
over the opening into the spur, so that an insect must push it on one side
to obtain honey. The anther contains two pollen-masses.

(vi) The ovary, at the top of which the shiny, sticky stigma is seen.
This is protected by the rostellum, which stands in front of it.

(vii) The pollen-masses can be extracted in the following way : With
a fine pointed pencil press the rostellum, and keep it pressed for
about twenty seconds. Now draw the pencil away slowly. On the
tip of the pencil the pollen-masses which have been extracted from the
anther lobes will be seen. Observe the pollen-masses ; at first they
are erect, but at the end of two or three minutes they incline forwards,
and if the pencil with the pollen-masses is placed in a second flower
they strike the stigma, and some of the pollen will adhere to it.

The flowers of the Spotted Orchis are splendidly adapted for
cross-pollination, as the last experiment shows. The smallest
quantity of pollen will obtain the maximum of results. If a bed
of this plant is watched on a bright day in June or July, the
bees will be seen to work the flowers for food, and if some of
the insects are caught and examined the pollen-masses will be
seen to adhere to their heads.

The Working of the Parts. — The bee or other insect which is
attracted to the Orchid flower lands upon the labellum on the
lower side of the flower. He passes his proboscis down into the
spur in search of honey. The head of the insect thus comes in
contact with the rostellum, which gives way before the pressure
and the bee's head now rests against the anther. The base of
the pollen-masses comes in contact with the head of the insect
and begins to set there. This process requires time — several
seconds at least. The time necessary for this to take place is
gained by the honey being stored up in the thickness of the
walls of the spur. To get the honey the proboscis has to dig and
penetrate the walls of the spur. This takes time, during
which the pollen-masses set on the head of the insect. When
the honey has been extracted, the insects fly away with the
pollen-masses, which change their position, as they did on the

214

BOTANY FOR BEGINNERS

CHAP.

pencil ; and when the next flower is visited, they come in contact
with the stigma and pollinate it.

4 — Flowers Pollinated by the Humble-Bee. — Flowers like the
Clover, Vetch, and Pea are pollinated by the humble-bee, which
possesses a longer proboscis than most insects. In flowers of
this description the honey is stored deep down the tube formed
by the diadelphous (p. 185) stamens.

EXPT. 1 88. — Obtain a few inflorescences of the Clover and examine
them. Note —

(i) The inflorescence is a head of numerous flowers,
(ii) Each flower is zygomorphic (p. 179).
(iii) The calyx is gamosepalous (p. 183).

(iv) The corolla is polypetalous (p. 183), and consists of a standard,
wings, and a keel.

(v) The stamens are diadelphous
(p. 185), and ten in number.

(vi) The pistil is monacarpous
(p. 186).

(vii) The free stamen and small
opening down which the humble-bee
can pass its proboscis.

(viii) If the standard is pressed
downwards, the stamens move so as to
discharge their pollen in a certain way.
(ix) There is only one way in which
honey can be extracted from the nectary
at the base of the tube formed by the
stamens.

Cross-pollination by the
Wind. — A large number of plants
are pollinated by the wind. They
include the great class of Grasses,
the -Hazel, Yew, Oak, and Plantain.
The chief characteristics of wind-
pollinated flowers are as follows : —

1. The flowers are small, simple,
and inconspicuous, thus presenting
a great difference to the brightly-
coloured insect-pollinated flowers.

2. The flowers have no scent

and do not secrete honey ; in fact, they have none of the
characters by which the entomophilous flowers attract insects.

FIG. 212. — Inflorescence of Plan-
tain, with protogynous flowers.
The upper flowers are closed, and
the styles hang out ; the lower
flowers have lost their styles, and
the stamens hang out. (S.)

xvr POLLINATION AND FERTILISATION 215

3. The flowers produce great quantities of pollen, which is
powdery and can easily be distributed by the wind.

4. The versatile anthers are fixed on to slender filaments,
which hang out of the flowers so that a little wind can shake
them. (Fig. 212) The Nettle, for instance, can distribute its
pollen from the anthers by uncurling its filaments with a sudden
movement and scattering the pollen in a minute explosion.

5. The stigmas are large and possess structures for holding
the pollen which comes in contact with them. (Fig. 212)

Comparison 'of Insect-Pollinated and Wind-Pollin-
ated Plants.—

Insect- Pollinated.

(1) The pollen is carried in a
definite direction, i.e., from flower
to flower.

(2) Less pollen is produced, for
it is more certain of performing its
work.

(3) The pollen is better pro-
tected from rain, dew, and
marauding insects. *

(4) Less material is used in
producing pollen.

(5) The maximum number of
seeds are produced with the mini-
mum amount of material.

Wind- Pollinated.

(1) The pollen is. carried in all
directions, and the great bulk of
it is lost.

(2) Large quantities of pollen
are produced, most of which never
reaches the stigma of a flower.

(3) The pollen is not so well
protected from the rain and dew.

(4) Less material is used in pro-
ducing showy flowers and honey.

(5) The maximum number of
seeds are produced with the maxi-
mum amount of material.

Self-Pollinated Plants.— By self-pollination is meant
where the pollen of a flower A pollinates the stigma of the same
flower A. There is a number of plants which produce flowers
that are always self-pollinated. Self-pollination is easily secured,
and seems in these flowers to give good results. The self-
pollinated plant is more likely to be pollinated than any other,
because the pollen is near at hand and only needs a little
movement to bring it on to the stigma. Either the wind or
insects may produce self-pollination, by distributing the pollen
from the anthers to the stigma. Several flowers, which are near
relations of the Daisy, have stigmas which curl downwards
until the pollen-ladened anthers are reached and self-pollination
takes place. The Poor-man's Weatherglass produces flowers
which may be cross-pollinated during the first three days after
opening. If not pollinated during this interval, the flowers

216 BOTANY FOR BEGINNERS CHAP.

close up and never open again, but the anthers come in contact
with the stigma and self-pollination takes place.

A very large number of plants produce two kinds of flowers —
the ordinary open ones and minute closed ones.

The small closed flowers, called Cleistogauiic flowers, are self-
pollinated and produce large quantities of seeds. The structure
and advantages of cleistogamic flowers must now be considered.

The Structure of Cleistogamic Flowers.— They are
very small and never open. The petals are rudimentary or
absent, the stamens few in number, the anthers small, the pollen
grains are few, producing their tubes while in the anthers, the
pistil is small, and the stigma almost absent. Pollination takes
place by the pollen tubes passing from the anthers down the
short style to the ovules in the ovary.

Advantages of Cleistogainic Flowers. — They seem to furnish
the following desirable results to the plant.

1. They produce seeds in seasons when the ordinary flowers
which are insect-pollinated might be able, to produce none.

2. They produce seeds with the smallest consumption of
matter, and the energy used is reduced to a minimum. The
amount of pollen used in the cleistogamic flowers of the Violet
is only the ^isVoo Part °f t^* usec^ by a Dandelion. Just
as many seeds being produced as in a perfect flower of the
Violet.

3. They belong to plants which also produce zygomorphic
flowers which are pollinated by insects. But insects, in this
strange climate of ours, are very variable quantities. Hence
seasons might occur, and do occur, when the necessary insects
not being present no seeds would be formed but for the
cleistogamic flowers.

Among the plants which produce cleistogamic flowers' are
the Wood-Sorrel, Violet, and Pansy.

Fertilisation. — When the pollen grains are deposited on
the stigma, they are generally held fast by its sticky surface.
The grains take up moisture and nutritive materials from the
stigma, and germination commences. Pollen tubes are pro-
duced, and these pass between the superficial cells of the stigma
and bore their way down the style. They feed, as they grow,
upon the tissue of the style, and enter the ovary. In the ovary
they find their way to the micropyles of the ovules. Each

POLLINATION AND FERTILISATION 217

ovule requires one pollen grain to form a tube to bring its

generative nucleus to the oosphere. Why the pollen tubes

enter the micropyle is not fully understood at present, but there

must be some substance which attracts them.

The pollen tube is guided to the oosphere by

the egg-apparatus (p. 201), the tip of the tube

is broken off, and the generative nucleus and

some of the protoplasm is set at liberty. The

liberated generative nucleus fuses with, and

fertilises, the oosphere.

In the Lily, the large size of the pollen grain
and tube enables all the stages in the produc-
tion of a pollen tube and in the process of FKJ ^ _pT oj
fertilisation to be followed. The vegetative 'kn 'tube ;' N,
nucleus passes into the pollen tube first, the grammat§la
generative nucleus following on. The vegetative
nucleus is used up during the growth of the pollen tube, and
the generative nucleus or cell divides into two. When the
micropyle is reached, the tube passes in between the egg-
apparatus, and the leading generative nucleus passes out at the
end of the tube along with some of the protoplasm. The nucleus
travels on until it reaches the nucleus of the oosphere, when
it fuses with it, the protoplasm uniting with the protoplasm of
the oosphere. After fertilisation, the oosphere becomes the
oospore or egg-spore, and it surrounds itself with a firm cell-
wall.

Development of the Embryo.— The development of the
embryo can be studied in a little wayside weed, the Shepherd's
Purse. This plant is self-fertilised and produces a very large
number of seeds, and as a rule, all stages can be obtained on
one plant, from the oospore up to the mature embryo.

The oospore divides into two cells. The one nearest the
micropyle is called the upper cell. The upper cell produces a
row of cells called the suspensor ; the lower cell by division gives
rise to nearly all the embryo. The suspensor supports the
embryo and fixes it to the wall of the ovule. The embryonic or
lower cell divides into eight cells. The four which are the greatest
distance from the suspensor form the cotyledons and plumule,
the four nearest the suspensor form the radicle. The tip of the
radicle and the root-cap are formed by the upper cell of the

218

BOTANY FOR BEGINNERS

CHAP.

suspensor. (Fig. 214) The outer cells of the embryo, as it can
be called, divide up to form the dermatogen (p. 112), which

forms the whole epi-
dermis of the plant.
The inner cells divide
up to form the picromc,
from which the central
cylinder of the main
stem is formed. Cells
are produced between
the dermatogen and
plerome, from which
the cortex is produced.
These form the peri-
blem.

EXPT. 189. — From the
Shepherd's Purse pull off
a number of ovaries in
different stages of deve-
lopment. Remove the
wall from a young ovary,
and with needles separate
some of the ovules from
the replwn or central
dividing wall of the ovary.
Soak some of the ovules
in potash solution for ten
minutes, or until they are
almost transparent.

Mount them in a drop
of glycerine on a slide and
place on a cover-glass.
Press, or give the cover-
glass a sudden tap, to
burst the ovules and force
out the embryos. Use the
low power for the older
stages and for the younger
ones the high power.
Note—

(i) The suspensor, which
consists of several cells, at
the end of which the em-
bryonic cell will be seen.

(ii) The embryonic cell in an older specimen will have divided into a
number of cells.

FIG. 214. — Stages in the development of embryo of
the Shepherd's Purse, c,. cotyledons \p, plumule ;
et, suspensor ; A, hypophysis. (Magnified.) (S.)

XVI

POLLINATION AND FERTILISATION

219

(iii) In a still older specimen the cells have become so arranged that
the following layers can be seen — (a) Dermatogen, covering most of the
embryo ; (b) plerome, forming the central
mass of embryo ; (c) periblem, between the
two.

,(iv) In still older stages the cotyledons
will have appeared. They will be seen as
lateral outgrowths from the upper part of
the embryo.

EXPT. 190. — Collect a few inflorescences
of the Water Plaintain (Alisma Plantago].
They are in full flower in June, July, and
August. The flowers are small and pink in
colour. Remove some of the ovules, and
treat with potash solution. Mount in
glycerine, and with the cover-glass force
out some of the embryos. Note —

(i) The suspensor and embryonic cell.

(ii) The embryonic cell divides up into
four cells.

(iii) The cells divide into dermatogen,
plerome, periblem.

^iv) Try and make out the following
structures—

(a) The single cotyledon which is formed
from the free end of the embryo ; (b) the
radicle and apex of root which are formed
from the lower cells.

Changes in Embryo -Sac.—

During the development of the em-
bryo, changes are taking place in the embryo-sac. The
embryo-sac nucleus (p. 203), divides up and produces a number
of nuclei. When hundreds of nuclei have been produced, and
the embryo- sac has been enlarged, cell- walls begin to be formed
between them. Thus, a tissue of parenchyma cells is produced
in the embryo-sac, in which starch and proteids in the form of
aleurone grains are stored up for the use of the embryo. This
tissue receives the name of endosperm. In Wheat, Barley, and
Rye, the endosperm is stored up in such quantities that it is
not all used up in the development of the embryo, but is
utilised when the seed germinates and the embryo begins to
grow. If the ripe seed contains endosperm it is said to be
albuminous. If the endosperm is all used up by the develop-
ing embryo, so that the embryo-sac is filled with the embryo, the
seed is said to be exalbuminous* Wheat, Barley, and Rye are

FIG. 215.— Young embryo of
the Water Plantain. C,
cotyledon ; v, growing
point. (Magnified.) (S.)

220 BOTANY FOR BEGINNERS CHAP.

examples of albuminous seeds, -and Peas and Beans of exalbum-
inous seeds. In a few cases, reserve material is formed from
the nucellus (p. 201), which is around the embryo-sac, when
the tissue formed is called perisperm. Examples — Henbane and
Piper.

Results of Fertilisation. — The fertilisation of the oosphere
has far-reaching results. These are shown below in a tabular
form.

1. The oosphere is converted into an oospore, from which, by
development, the embryo is produced.

2. The embryo-sac is filled with endosperm, which may be
used up by the developing embryo or stored up until the seed
germinates.

3. The ovule is converted into a seed.

4. The ovary is converted into a fruit.

SUMMARY.

Flowering Plants differ from non-flowering plants in the production
of seeds.

Seeds are formed from ovules by the changes which go on after
fertilisation.

Pollination is the distribution of the pollen from the anther to the
stigma, It can take place in two different ways — (i) Cross-pollination,
when the pollen of A finds its way to the stigma of B ; (ii) Self-pollina-
tion, when the pollen of A finds its way to the stigma of A.

Contrivances to Prevent Self-Pollination . These are— (i) The flowers
may be diclinous (p. 208) ; (ii) the plants may be monoecious or
direcious (p. 208) ; (iii) the flowers may be protandrous or proto-
gynous (p. 209) ; (iv) the plant may produce two or three kinds of
flowers ; (v) the pollen of A may have no effect on the stigma of A.

Insect-Pollinated flowers are — (i) Brightly coloured, sweet scented,
and very prominent ; (ii) they produce either honey, or plenty of
pollen, or both ; (iii) their pollen is sticky ; (iv) their stigmas are
small.

Dimorphic Plants produce two kinds of flowers ; these are — (i)
Flowers with short-styles ; (ii) flowers with long-styles.

The pollen of the short-styled form pollinates the stigma of the long-
styled form, and the pollen of the long-styled flower the stigma of the
short-styled form.

Trimorphic Plants produce three kinds of flowers ; these have three
lengths of style.

Humble-Bee F/oivers, such as the Clover, Vetch, and Pea, cannot be
pollinated by any other insect because their tongues are not long
enough.

Wind-Pollinated Plants produce flowers which possess the following
characters — (i) The flowers are small, and generally green ; (ii) the

POLLINATION AND FERTILISATION 221

flowers have no scent ; (iii) the flowers produce great quantities of

pollen which is dry ; (iv) the anthers are versatile and hang out of the

flower ; (v) the stigmas are very large.

Self-Pollinated Plants produce flowers which may be —

(a) Pollinated by the wind blowing the pollen from the anthers to the

stigma of the same flower.

(6) Pollinated by insects creeping over the flower and distributing the

pollen from the anthers to the stigma of the same flower.

(d) Pollinated by the flower never opening — cleistogamic flowers.
Fertilisation is the union of the generative nucleus of the pollen grain

with the oosphere in the ovule.

The Embryo Develops from the oospore by division.

The Results of Fertilisation are—

(i) The oosphere changes into the oospore.

(11) The oospore changes into the embryo.

(iii) The embryo-sac is filled with a tissue — the endosperm,
(iv) The ovule is converted into a seed,
(v) The ovary is converted into a fruit.

QUESTIONS ON CHAPTER XVI.

1 i ) Explain, giving examples, the meaning of the following terms-
dioecious, monoecious, diclinous, hermaphrodite, complete. (1897.)

(2) What is meant by self-fertilisation and by cross-fertilisation?
Mention any plants in which the wind is the agent in pollination. ( 1891. )

(3) Describe the structure of the flower of any British Orchid, and
explain how pollination takes place. (1890.)

(4) Mention three different flowers which are not pollinated by
insects, and explain in what respects they differ from flowers which are
so pollinated. State the means by which the pollination of these three
flowers is effected. (1894.)

(5) Explain the way in which insects are of use to flowers, and the
means by which flowers attract them.

(6) In what important respects do wind-fertilised flowers differ from
insect-fertilised flowers? Give examples of both. (1898.)

(7) Explain briefly the biological significance of (a) brightly coloured,
and (b) irregular flowers, as compared with (c) inconspicuous and (d)
regular flowers. Give examples.

(8) What is the use of the spurs formed from floral leaves ? Give
examples.

(9) What is meant by heterostyled plants? Give examples.

(10) Mention plants which produce cleistogamic flowers, and explain
of what use they are to the plant.

(n) How do dimorphic plants differ from trimorphic plants ? Explain
what advantage (if any) the trimorphic plants will have over the
dimorphic plants.

(12) Why are the pollen-grains larger in the short-styled flower of the
Primrose than in the long-styled form ?

CHAPTER XVII

THE MORPHOLOGY OF SEEDS AND FRUITS, AND THEIR
DISTRIBUTION

Seeds. — A seed is the result of the changes which take
place in an ovule after fertilisation. The changes can be shown
thus :—

(1) The oospore develops into an embryo.

(2) The embryo-sac nucleus divides up to form endosperm.

(3) The coverings or integuments of the ovule change and
become fit for the protection of the embryo, and in the seed are
called the spermoderm (p. n.)

Structure of Seeds.— Each seed is covered with a layer,
the testa. It is formed from the integuments of the ovule.
The central portion of the seed consists of the embryo and the
endosperm when it is present. The opening through the testa
is called the micropyle (p. 10), and represents the micropyle of
the ovule. The parts present in albuminous and exalbuminous
seeds may be shown thus : —

Seeds.

Albuminous. Exalbuminous.

Testa. Testa.

Embryo. Embryo.

Endosperm.

Comparison of an Ovule with a Seed.— The corres-
ponding parts of the ovule and seed may be easily compared : —

CH. xvii MORPHOLOGY OF SEEDS AND FRUIT

223

Ovule,
Funiculus.
Integuments.
Micropyle.
Nucellus.
Embryo-sac.
Contents of sac.

Seed,

Funiculus.
Testa.
Micropyle.
Perisperm.
Embryo-sac.
Embryo and Endosperm.

Examples of Various Kinds of Seeds.— Some examples of the different
kinds of seeds will be useful : —

Albuminous.

Exalbuminous.

With Perisperm.

Wheat.

Pea.

Stellaria.

Barley.

Bean.

Piper.

Violet.

Mustard.

White Water Lily.

Rye.
Tulip.

Apple.
Chestnut.

Henbane.

Castor Oil.

Oak.

Buttercup.

All Grasses.

The ' Aril. — The seeds of some plants have appendages
which may be variously produced from the funiculus, hilum, or
micropyle. Such new growths are called arils. In the Willow-
herb a tuft of hairs is produced which aids in the distribution
of the seeds. In the Water Lily the aril is produced from the
funiculus, and grows round the seed, producing an outer cover-
ing often mistaken for the integument. This method of the
formation of an aril also takes place in the Yew and Passion
flower. In the seed of the Castor Oil plant the aril appears as
a small ivart-like swelling at its base. The Willow produces a
tuft of woolly hairs formed from the funiculus, and hence called
a funiculus aril. Among other plants which produce an
aril Milkwort, Violet, Celandine, and Spindle-tree may be
mentioned.

EXPT. 191. — Examine the structure of the seeds given in the table
on p. 223. Note —

(i) The nature of the testa.

(ii) The position of the hilum and micropyle.

(iii) The kind of seed — whether albuminous or exalbuminous.

(iv) The nature of the endosperm or perisperm.

(v) The number of cotyledons present.

224

BOTANY FOR BEGINNERS

Fruits. — Fertilisation not only stimulates the ovule and its
contents so that a seed may be produced, but its influence also
extends to the carpels, and in some cases to other parts of the
flower, so that a fruit is formed. Other parts of the flower
which do not take part in the formation of the fruit drop off
sooner in cases where fertilisation has not occurred. A fruit is
the direct result of the changes which go on in a flower as a
result of fertilisation.

Definition of a Fruit. — A true fruit is the result of the
changes which go on in a single gyncecium due to fertilisation.
When other parts of the flower take part in the formation of

Trans verse Section

FIG. 216. — A, Apple ; E, longitudinal section of Apple ; C, transverse section of
Apple. E, endocarp; M, mesocarp ; En, endocarp ; S, seed.

the fruit, the organ produced is called a spurious fruit or
pseudocarp. The apple is formed by the receptacle growing up
round the gynoecium after fertilisation, and so forming the
whole of the succulent part of the fruit. When an apple is
used as food, it is the altered receptacle and calyx which we
eat. The central part is formed from the gynoecium and is
called the core. The pips are the seeds. (Fig. 216.)

In the strawberry the receptacle becomes succulent after
fertilisation, and carries up the true fruits — the hard grains
which the fruit contains (Fig. 217). Fruits can thus be divided
according to the parts of the flower which take part in their
formation into true fruits and spurious fruits.

XVII

MORPHOLOGY OF SEEDS AND FRUIT

225

Structure of a Fruit. — The wall of the fruit is called the
pericarp, and in most instances it can be divided into three
different layers : —

Theefocarfl, or outer layer of the fruit. (Fig. 218).

The mesocarp, or middle layer of the fruit.

The endocarp, or inner layer of the fruit.

The pericarp may be hard and dry, or soft and succu-
lent ; in a few cases a portion may be succulent and the
remainder hard. In the Plum and Cherry the epicarp and
mesocarp are succulent, and the endocarp is hard (Fig. 218).
The Hazel-nut possesses a very hard pericarp which is broken
off when the seed within is used for food (Fig. 221).

When the fruit is formed from a single carpel, as in the

-R

Ac-"

FIG. 217. — A1, Strawberry; B1, longitudinal section of Strawberry; Ac, carpel;
R, swollen receptacle.

Bean and Pea, it is called a monocarpous fruit. If two or more
separate carpels take part in the formation of the fruit, as in the
Buttercup and Raspberry, the fruit is apocarpous. A syncarpous
fruit is formed from a syncarpous gyncecium, as in the Poppy,
Lily, and Wallflower.

Fruits may dehisce or open to liberate the seeds, when they
are called dehiscent fruits. If the fruits do not open to liberate
the seeds, but the seeds germinate within, and the young plant
break through the wall of the fruits, they are called indehiscent
fruits.

When the fruit is the result of a single gynoecium it is called
a simple fruit, and when produced from a number of carpels it
is said to be a compound fruit. Thus, both monocarpous and
syncarpous fruits are simple, while apocarpous fruits are
compound.

226 BOTANY FOR BEGINNERS CHAP.

EXPT. 192. — Select a ripe Cherry and examine it. Note—

(i) It is fixed on the top of a stalk — the peduncle.

(ii) Just below the fruit a scar is present ; this is where the stamens
were attached. The calyx must have been inferior.

(iii) Just on the top of the fruit a small spot is present ; this is where
the style was fixed.

(iv) The Cherry must be a true fruit because it is formed from the
gyncecium only.

Cut the fruit across. Note —

(v) The hard stone in the middle ; the hard part is the endocarp.

(vi) The pulp, or succulent part, which consists of two layers ; the
outer of these is the epicarp, and the inner the mesocarp.

Now break open the stone. Note —

(vii) The seed in the centre ; it is protected from injury by the hard
endocarp.

(viii) Stone fruits like the Cherry, Plum, and Peach are called drupes.

EXPT. 193. — Obtain a ripe Gooseberry and examine it. Note —

(i) At the top of the fruit the dried-up lobes of the calyx occur. This
shows that the fruit is inferior.

(ii) The fruit is succulent, and when ripe the pulp can be forced out.

Now cut across the middle. Note —

(iii) The fruit is one-celled, and the cavity is filled with juicy pulp
containing a number of seeds.

(iv) All fruits which are syncarpous -and succulent, and do not open to
liberate the seeds, are called berries. Thus, the fruits of the Red and
Black Currants and Grapes are all true berries.

EXPT. 194. — Obtain a Poppy head from a chemist and examine it.
Note—

(i) The external markings on the fruit ; these represent the carpels
from which the syncarpous fruit was formed.

(ii) If the fruit is shaken, seeds fall out through pores which are near
the apex. When fruits liberate their seeds by pores, they are said to
dehisce by pores.

Now cut across the fruit. Note —

(iii) The syncarpous fruit is one-celled and contains many seeds.

(iv) A dry syncarpous fruit which dehisces by pores, valves, or teeth
is called a capsule.

EXPT. 195. — Examine an Apple. Note —

(i) The remains of the lobes of the calyx on the top of the fruit: The
fruit is inferior.

Now make a section of the Apple so as to pass through the dried
lobes of the calyx and the peduncle. Note —

(ii) The skin, which is peeled off when the Apple is eaten, is the
epicarp.

(iii) The succulent part of the pericarp, which is eaten, is the
mesocarp.

(iv) The core is the endocarp and contains the seeds.

XVII

MORPHOLOGY OF SEEDS AND FRUIT

227

(v) The calyx tube, or receptacle, has grown up and surrounded the
gyncecium, thus forming a spurious fruit. The spurious fruits like the
Apple are called pomes.

EXPT. 196. — Obtain a number of Strawberries in different stages of
development, and examine them. Note —

(i) The ripe Strawberry consists of a pulpy mass which is surrounded
at its base by the persistent calyx.

(ii) The surface of the fruit is covered by numerous small bodies
which are the carpels of the apocarpous gyncecium. Each one bears a
a style or shows the scar where the style was fixed.

Now examine the series of Strawberries. Note —

(iii) The least ripe Strawberry will have a very small receptacle,
while in riper ones the receptacle increases in size. Thus, the fruit of
the Strawberry is spurious, and is formed by the receptacle becoming
succulent.

(iv) It is an apocarpous spurious fruit.

EXPT. 197. — Examine a Blackberry and compare it with the Straw-
berry. Note —

(i) The Blackberry consists of a number of succulent druplets, which
are arranged on a slightly enlarged receptacle.

(ii) Each druplet contains a seed.

(iii) It differs from the Strawberry in having the carpels succulent
instead of the receptacle.

(iv) The Blackberry is an apocarpous fruit, and may be called a
compound drupe.

Classification of True Fruits.— Fruits can be arranged
according to the characters of the ripe pericarp into : —

( i ) Succulent fruits (simple), when some portion or the whole
of the pericarp is succulent.

FIG. 218.— A, Plum ; B, longitudinal section ; C, transverse section. E, epicarp ;
M, mesocarp ; En, endocarp ; S, seed.

(a) The drupe, when the epicarp and mesocarp are succulent,
but the endocarp is hard and stone-like (Fig. 218). Examples
— Cherry, Plum, Peach, and Apricot.

Q 2

228

BOTANY FOR BEGINNERS

CHAP.

(£) The berry, when the whole of the pericarp is soft and
succulent (Fig. 219). Examples— Gooseberry, Grape, Currant,
Orange, and Cucumber.

FIG. 219.— A, Gooseberry ; B, longitudinal section ; C, transverse section.

Collective Fruits. — (c) The compound druplets, when the
carpels of an apocarpous gyncecium are succulent, separated,
and each contains a seed (Fig. 220). Examples — Blackberry
and Raspberry.

(2) Dry fruits, when the pericarp is hard and dry. If they
do not open to liberate the seeds they are indehiscent ; if they
open, they are dehiscent.

FIG. 220.— Black- FIG. 221.— A, Group of Hazel nuts ; B, longitudinal section

berry. of fruit. (One-half nat. size.)

Indehiscent Fruits.— (a) The nut is hard, inferior and
syncarpous (Fig. 221). Examples— Acorn, and Hazel-nut.

(b] The achene is hard, superior, and consists of one carpel
(Fig. 222). Examples — Buttercup and Rose.

XVII

MORPHOLOGY OF SEEDS AND FRUIT

229

many one-seeded fruits, and these enclose the seeds until
germination (Fig. 223). Examples — Fool's Parsley, Maple, and
Geranium.

FIG. 222.— Achenes of Buttercup. (S.) FIG. 223.— Schizocarp of Sycamore.

Dehiscent. — (a) The capsule is a dry, syncarpous fruit which
opens by pores, valves, or teeth (Fig. 224). Examples — Poppy,
Lily, Foxglove, and Stellaria.

FIG. 224.— A, Capsule of Poppy ; B, transverse section of capsule ; C, seeds. (One-
fourth nat. size.)

(V) The siliqua is formed of two carpels ; it is superior and
syncarpous (Fig. 226). Examples — Wallflower, Rape and
Mustard.

If the siliqua is short and wide it is called a Siiicula. Ex-
ample— Shepherd's Purse (Fig. 227).

230

BOTANY FOR BEGINNERS

CHAP.

dehisces along both the ventral and dorsal sides (Fig. 225).
Examples— Pea, Bean, Vetch, and Clover.

(Vf> The follicle consists of a single carpel which dehisces

FIG. 226.— A, Fruits of
Wallflower ; B, siliqua;
C, siliqua open.

FIG. 227. — A, Fruits of Shep-
herd's Purse ; B, silicula ; C,
transverse section across B.

FIG. 228.— Folliclt
of Monkshood.

along the ventral side only (Fig. 228).
Aconite, Poeony, and Larkspur.

Examples — Columbine,

EXPT. 198. — Collect a few Hazel-nuts and examine one. Note —
(i) The hard, dry pericarp which encloses the seed,
(ii) The pericarp, if broken open, shows three layers, which represent
the epicarp, mesocarp, and endocarp.

(iii) The fruit is syncarpous and indehiscent.

xvn MORPHOLOGY OF SEEDS AND FRUIT 231

EXPT. 199. — Collect a few fruits from the Broom and examine them.
Note—

(i) The fruit is superior, and often bears at the tip the remains of
the style.

(ii) The top of the stalk bears the remains of the calyx.

(Hi) The fruit is monocarpous, and will split open along both sides,
or sutures.

(iv) The fruit is a legume.

EXPT. 200. — Collect a few full-blown Buttercup flowers and examine
the fruit. Note —

(i) The fruit consists of a number of carpels. Each carpel is dry,
indehiscent, and contains a single seed.

(ii) Fruits of this description are called achenes.

Distribution of Seeds. —Just as the variety of colour,
form, and perfume of flowers have to do with the distribu-
tion of the pollen, so the variety of texture, colour, and shape
in fruits have to do with the distribution of seeds. Plants are
stationary objects, and to give the young plants a chance in the
struggle for existence, it is necessary that the seeds should be
distributed as widely as possible from the parent plant. When
it is considered that only a few seeds out of the large number
produced can possibly find suitable conditions for germination,
it will be realised that the distribution of seeds is an important
branch of the natural history of plants.

The fact that seeds are distributed from place to place is
shown by plants springing up in unlikely localities, such as
ruined buildings, on churches, and old walls. Some time ago
in examining the top of a church, a number of the seeds of the
Sycamore were found. These were germinating, and most
likely had been carried for a considerable distance by the wind.
Had a suitable soil been present, it seemed possible for some
of the Sycamore seeds to have taken root and flourished. So
numerous are the plants which sometimes grow in such places
that lists have been prepared of the vegetation found on Cologne
Cathedral, the Coliseum at Rome, and for many other places.

How Seeds are Distributed.— Seeds may be distributed
in many ways : —

(1) The seeds or fruits may be scattered by the wind.

(2) The seeds may be scattered by the fruit exploding, and
so sending individuals for a considerable distance from the
parent tree.

232

BOTANY FOR BEGINNERS

CHAP.

(3) The seeds or fruits may be scattered by clinging to the
wool or hair of animals.

(4) The seeds and portions of the fruits may be scattered by
animals swallowing them ; after passing through their bodies,
the seeds may germinate.

Seeds Scattered by the Wind.— The seed or fruit
often has wing-like appendages which make their superficial
area greater and so much lighter in proportion to their bulk.
When seeds or fruits of this kind are liberated from the parent
plant, they fall slowly through the air, not straight down, but in
zigzag lines, like the movements of a roolc or lapwing, through
the air.

The pappus of hairs which is produced from the calyx in the
Dandelion aids in the dispersal of the fruits. In the Poppy and
Larkspur the seeds lay loose at the bottom of the fruits, and
when the wind blows the fruit from side to side the seeds are
gradually distributed far from the parent plant. The following
table shows how a number of common seeds and fruits are
scattered by the wind : —

i. The fruits of the Ash, Sycamore, Elm, and Birch, have
appendages which carry them for a long distance from the
parent plant.

FIG. 229.— Fruit of Dandelion. FIG. 230.— Ripe fruit of Sycamore.

2. The fruits of the Dandelion, and most Composite possess
a pappus of hairs, and are in this way carried through the air
by the wind.

XVII

MORPHOLOGY OF SEEDS AND FRUIT

233

3. The seeds of the Willow, Poplar, and Willow-herb, have
tufts of hair, which act like the pappus of the Dandelion.

4. The seeds may be winged, as in the Begonia.

5. The seeds may be small or flattened in form, as in the
Orchid, Poppy, Larkspur, and Wallflower, when they are
scattered by the wind blowing them out of the fruits.

Seeds Scattered by Explosive Fruits.— Explosive
fruits are not common, but the following examples will illustrate
their action. In the Box, the seeds are smooth, and are dis-
charged by the pericarp contracting and forcing the seeds out like

FIG. 231. — Violet. F, explosive fruit ;
S, seeds being shot out of fruit.

FIG. 232.— Wood Sorrel. F, sling
fruit ; S, seeds being slung out of
fruit.

a bean shot from between the fingers. The capsule of the Violet
splits open, and, as the valves dry, they contract and fling out
the seeds. In the Wood-Sorrel and Squirting Cucumber, the
fruit dehisces suddenly, and ejects the seeds for a considerable
distance.

Seeds Scattered by Clinging to Animals.— Plants
may produce fruits, and in a few rare cases seeds, which are
armed with hooks, by which the seeds adhere to the hair or
wool of animals. A most familiar example is the Galium, which
grows in many of the hedgerows in the country lanes through-
out the United Kingdom. Fruits which are armed with hooks

234

BOTANY FOR BEGINNERS

CHAP.

receive the name of burrs. The hooked fruit of the Wood
Avens clings to animals, and is carried for great distances. A

country walk through a district
where these plants grow will best
show how their fruits are distri-
buted by animals.

Seeds Scattered by Ani-
mals.—When seeds are distributed
by passing through the alimentary
canal of animals, they must possess

C\ "** two characters, (a) The seed must

^^^r- J^l ^e protected by a hard portion of

// the fruit, which is not acted upon

by the digestive juices during the
passage of the fruit through the
alimentary canal, (ff) The hard
part of the fruit must be surrounded
by something eatable to tempt the
animal to swallow it. The drupes
of the Cherry, Blackberry, and
Raspberry, are scattered by birds
eating them and afterwards drop-
ping the seeds. As a rule, plants which produce fruits that are
adapted for distribution in this way produce succulent fruits, as
the Apple, Strawberry, Rose-hips, and Currant.

(Termination of Seeds. — The conditions necessary for
the germination of seeds have already been considered (p. 152).
That seeds have their vital functions arrested by drying is
familiar to everyone ; but when seeds are placed under suitable
conditions germination soon begins. Seeds and fruits are able
to find a permanent lodgment in the soil by the structure of
their surfaces. Thus, the fruits of the Geranium and Grasses
are enabled to bury themselves in the ground by movements
which are produced by changes in the amount of moisture they
contain. The Ivy-leaved Toadflax, or Mother of Thousands,
buries its seed capsules in the crevices of walls and cliffs. Nuts,
Acorns, and similar seeds are often buried in the ground by
animals, such as the squirrel, and forgotten. Afterwards they
may germinate. Some seeds have mucilaginous coverings,
which not only fix them to the soil but absorb water.

FIG. 233. — Fruit of Wood Avens.
A, the fruit, showing the hook
H ; B, the fruit, with both
style and stigma ; C, the style
and stigma more highly magni-
fied. The hook is formed from
the style by the stigma break-
ing away.

xvn MORPHOLOGY OF SEEDS AND FRUIT 235

EXPT. 201. — Place some seeds of the Pumpkin on damp sawdust,
and examine them from time to time. Note —

(i) The seed is flattened, oval in outline, and possesses a thickened
border. At one end the hilum and micropyle occur. Split open the
cotyledons ; observe it is an exalbuminous seed.

(ii) The young radicle (when it appears through the micropyle) grows
downwards and fixes itself in the soil.

(iii) The young radicle possesses a peg or projection on the lower
side which pins down the seed-coats while the cotyledons are extracted.

(iv) The hypocotyledonous portion, when it comes out of the seed, is
arched ; this enables it to lift the soil far better than if it came up
straight.

(v) The cotyledons increase in size, open out, and perform the work
of assimilation.

EXPT. 202. — Compare plants in various stages of germination.
Note —

(i) The embryo swells and bursts the testa.

(ii) The radicle comes out of the micropyle and curves downwards and
enters the soil.

(iii) The hypocotyledonous stem, or portion beneath the cotyledons,
comes up curved.

(iv) The cotyledons are green even beneath the ground. They
elongate and spread when exposed to light.

(v) The plumule develops and produces the foliage leaves.

SUMMARY

Changes in the Embryo-sac form the endosperm, and convert the
ovule into a seed. Seeds may be albuminous, i.e., have endosperm and
embryo in the embryo-sac ; or exalbiuninous, i.e., have only the embryo
in the embryo-sac.

The Seed is covered with a testa which encloses the embryo and also
the endosperm if it is present.

The Aril is a growth formed from some part of the ovule.

Fruits are divided into true fruits and spurious fruits. A true
fruit is formed from a single gyncecium. In a spurious fruit some
other portion of the flower takes part in its formation. The wall of
fruits is called the pericarp, which can be divided into epicarp, meso-
carp, and endocarp. Fruits may either dehisce or open to liberate the
seeds, or they may not dehisce.

True fruits may be succulent or dry, and can be arranged into —

Succulent. Dry.

The drunlets The achene- The legume.

The schizocarp. The follicle.

The capsule.

236 BOTANY FOR BEGINNERS CH. xvn

Seeds may be distributed by the wind ; by explosive fruits ; by
clinging to animals ; by the digestive process of animals.

Fruits or seeds may have appendages which act the part of a para-
chute. Fruits may be armed with hooks which cling to the hair and
wool of animals ; or they may be succulent and so get eaten by animals,
the seed being afterwards dropped uninjured.

Seeds germinate when placed under suitable conditions. Some
plants bury their seeds, others provide the seeds with coverings which
enable them to bore their way into the soil.

QUESTIONS ON CHAPTER XVII.

1 i ) Explain precisely in what points of structure a seed differs from
an ovule. (1880.)

(2) What is a fruit? How does a true fruit differ from a spurious
fruit ?

(3) What is a berry ? What are the advantages to a plant to have this
kind of fruit? (1877.)

(4) Describe and compare the fruits of the following plants : — the
Buttercup, the Cabbage, the Gooseberry, the Orange. (1890.)

(5) Draw and describe the fruit of a field Geranium, and point out the
uses of some of its peculiarities.

(6) Describe the structure of the seed of the Buttercup, of the Apple,
and of the Onion. ( 1 89 1 . )

(7) Distinguish between albuminous and exalbuminous seeds, giving
an example of each. What is the use of the albumin ? (1894.)

(8) What is meant by the "dehiscence" of a fruit? Describe the
dehiscence of the fruit of the Marsh Marigold, the Pea, and the
Primrose.

(9) Describe and compare (a) the capsule and the berry, (b) achene
and drupe, giving an example of each. (1898.

(10) From what part of a flower may the fruit be developed? De-
scribe an achene, a follicle, and a nut, giving examples. (1889.)

( 1 1 ) Describe and compare the fruits of the Strawberry, the Raspberry,
and the Gooseberry. ( 1 893. )

(12) What is the aril? Describe the different forms of this structure
which are found in British plants. (1891.)

(13) Give examples of fruits and seeds which are dispersed by the
aid of birds and other animals, explaining in each case how the dispersal
is effected. (1893.)

CHAPTER XVIII

THE PHYSIOLOGY OF REPRODUCTION

Necessity for Reproduction.— Hitherto the means by
which plants maintain their individual lives have alone been
considered. The limited duration of the life of a single plant is
known to every one. Plants are not only preyed upon by slugs,
but larger animals also use them for food, and countless parasites,
too, live on them. Plants also struggle among themselves for
food and light. Extremes of cold and heat have to be con-
tended with. Plants live, die, and new ones take their place.
Given this fact that plants die, the subject of reproduction
becomes of vital interest, because it is the only way — as far
as is known — by which these new individuals can be produced.
All existing plants are the descendants of ancestral forms.

By reproduction is meant the production of new individuals by
an existing plant. This can take place in two ways : (i) By a
portion of the vegetative part of a plant being cut off from the
parent plant, thus forming a new individual. This method
of reproduction is called asexual or vegetative reproduction.
(2) By the union of two cells, one the male, the other the female.
These cells, by their fusion, form a single cell which is capable of
developing into a new individual. This method of reproduction
is called sexual reproduction.

Vegetative Reproduction.— This form of reproduction is
comparatively simple, and almost any part of the plant may
become separated to form a new individual. The branches of
the Gooseberry bend down, and roots are formed at the ends of
the branches, which become detached, and form independent
plants. The runner of the Strawberry creeps over the surface
of the soil for a considerable distance, and roots develop at its

238 BOTANY FOR BEGINNERS CHAP.

nodes. This ultimately forms an independent individual by the
intervening portion dying away. The off-set of the House-leek
becomes similarly detached, and forms a new plant. The stolon
of the Couch Grass performs the same function. In the axil of a
leaf of the bulb of the Tulip a new bud is formed which even-
tually exhausts the whole bulb, and carries on the life of the
plant. The Potato produces tubers at the ends of the stolons.
These tubers after a resting period develop into new plants.

The Pilewort and some of the Lilies produce small buds, which
receive the name of bulbils, in the axil of foliage leaves. These
bulbils contain stores of reserve material, and drop off the
parent plant to produce new individuals. The leaves of the
Begonia and other plants will, if they come in contact with the
soil, produce buds which develop into new plants.

The Biological Importance of Vegetative Reproduc-
tion.— As long as the food supply is plentiful, and the surround-
ings are favourable, vegetative reproduction suffices. It is an easy
way of ensuring the propagation of the particular races of
plants in which it is possible. Gardeners use this method on a
large scale for the production of any favourable character which
a plant may show. It is said that if vegetative reproduction is
indulged in for a long time by a particular race of plants there
is a tendency for the race to degenerate. Most plants, however,
also reproduce their kind by organs which are produced in a
sexual manner.

Sexual Reproduction. — The male reproductive cell is the
generative nucleus of the pollen grain, and the female cell the
oosphere in the embryo-sac. The former is called the male
pronucleus, and the latter the female pronucleus. Neither of
these cells can alone produce a nfew plant, but the actual repro-
ductive cell is formed by their union. The union of the male
cell with the female cell stimulates the cell formed, and it
develops into a new individual which combines the good or
bad characters of the parents. Sexual reproduction differs from
vegetative reproduction in the fact of the cells, which produce the
new plant, being formed in special organs — the pollen grain and
embryo-sac. The most important fact in sexual reproduction is
that in a single cell there should be stored up the potentiality of
the future plant, or in other words, a single cell should be able
to produce a perfect plant.

XVIII

THE PHYSIOLOGY OF REPRODUCTION

239

Death of,
Parent

The Biological Importance of Sexual Reproduc-
tion.— The biological importance of sexual reproduction cannot
be overestimated. As long as the surroundings of a plant are
favourable, vegetative reproduction suffices, but under unfavour-
able conditions, the life of the particular race of plants can only be
continued over the hard time by sexually produced bodies. The
seed produced as the result of sexual union is capable of retain-
ing its vitality under external conditions which would destroy
the mature plant. During a period of drought the vitality of
the young embryo within the seed is only suspended, not de-
stroyed, and when the ne-
cessary conditions again Germination
occur, it germinates and
produces a perfect plant.

Life -History. —All
the changes which a plant
undergoes from birth to
death are called its life-
history. The life-history
of an annual plant con-
sists of the germination
of the seed, the produc-
tion of the seedlings, its
growth to maturity, when
it flowers and produces
pollen and ovdles. The
generative nucleus of the pollen grain unites with the oosphere
in the ovule, and the oospore is formed. The oospore develops
into the embryo, and a seed is produced. The parent dies,
but the life of the particular race of plants is carried on by the
embryo in the seed.

The life -history of a biennial plant consists'of the germination
of the seed and the production of the seedling ; its growth and
the storing up of reserve material, which ends the first
year of its life ; then during the second year growth recom-
mences, and a flower stem and flowers are produced ; pollen
and ovules are formed ; these produce seeds, and the parent
dies too.

The life-history of a perennial plant takes three or more
years for its completion. It consists of the germination of the

FIG. 234. — Graphic illustration of the Life-
history of an annual plant.

240

BOTANY FOR BEGINNERS

CHAP.

ion of

seed, the production of the seedling, and its growth until
maturity is reached. Flowering then takes place, once or many
times, and seeds are formed. The plant may only live a few
years, or for a thousand years. It is a common thing to see

trees with several hun-
dred rings, which mark
so many years of growth,
and a section of the
Sequoia in the British
Museum has 1330 annual
rings. The life-history of
such a plant is shown in a
graphic manner in Fig.
'Material

Growth

236.

SUMMARY.

FIG. 235.— Graphic illustration of the Life-
history of a biennial plant.

The Necessity for Eepro-
duction is shown by the
death of the individual
plant. It is only by new

plants being produced that it is possible for a race of plants to con-
tinue. There are two ways by which new individuals can be pro-
duced-^) by vegetative re- Germination of
production ; (b) by sexual
reproduction.

Vegetative Reproduction
of a plant takes place by a
portion of the vegetative part
of the plant being severed
from the parent ; this leads
an independent life as a new
individual.

The Sexual Reproduction
of a plant is brought about
by the union of two cells ;
these by their union produce
one cell which develops into
the embryo.

The Biological import-
ance of Reproduction is
shown in the multiplication
of the individual, and by the better chance it gives the offspring by the
distribution of the seeds far away from the parent. The seeds pro-
duced can stand extremes of climate better than the mature plant.

The Life-History of a plant consists of all the changes which it under-
goes from birth to death.

FIG. 236.— Graphic illustration of the Life-
history of a perennial plant.

xviii THE PHYSIOLOGY OF REPRODUCTION 241

QUESTIONS ON CHAPTER XVIII.

1 i ) Give an account of the different ways in which plants propagate
themselves otherwise than by seed. (1898.)

(2) Why is reproduction necessary in plants? Enumerate the two
ways by which plants propagate themselves.

(3) Define what is meant by "sexual reproduction." How -does it
take place ?

(4) What is the biological importance of sexual reproduction ?

(5) Explain what is meant by the life-history of a plant.

(6) Trace the history of an annual plant from the time of the germin-
ation of the seed until it dies.

(7) How does the life-history of an annual plant differ from the life-
history of a biennial plant ?

(8) Show in a graphic manner the life-history of —

(a) An annual plant.

(b) A biennial plant.

CHAPTER XIX

THE CLASSIFICATION OF PLANTS

Natural System. — The natural system of botanical classifi-
cation is based on the resemblances and differences in plants, on
the structure, in fact, of both their vegetative and reproductive
organs. The whole plant kingdom can be divided into two
sub-kingdoms (i) Phanerogams, and (ii) Cryptogams. All
plants belonging to the former division produce flowers and
seeds, while those of the latter produce neither flowers nor
seeds. The Phanerogams are again divided into (a) Angio-
sperms and (b) Gymnosperms. The Angiosperms have
their ovules enclosed in an ovary, but the Gymnosperms have
naked ovules. The Angiosperms include two main classes (a)
Dicotyledons, and (fy Monocotyledons.

Dicotyledonous plants have the
following characters : —

The seedling possesses two seed
leaves or cotyledons.

The foliage leaves are reticulate-
veined.

The vascular bundles are open
and arranged to form a circle.

The parts of the flowers occur
either \r\fives, fours, or multiples
of these numbers.

Monocotyledonous plants have
the following characters : —

The seedling possesses but one
seed leaf or cotyledon.

The foliage leaves are parallel-
veined.

The vascular bundles are closed
and scattered.

The parts of the flowers are in
threes, or multiples of this number.

Divisions of Dicotyledons.— The dicotyledonous plants
can be arranged into four sub-classes, according to the structure
and arrangement of their floral whorls.

i. — Thalamiflorse. — All dicotyledonous plants which have
the stamens hypogynous (p, 185), and the pistil superior (p. 183).

CH. xix THE CLASSIFICATION OF PLANTS 243

(2) Calycifiorse. — All dicotyledonous plants which have the
stamens perigynous (p. 185) or epigynous, and the pistil either
superior or inferior.

(3) Gamopetalse.— All dicotyledonous plants with gamope-
talous (p. 184) corolla, and epipetalous stamens, the pistil is
either stiperior or inferior.

(4) Incomplete. — All dicotyledonous plants with the corolla
absent.

Divisions of Monocotyledons. — The monocotyledons
are arranged into three sub-classes, according to the structure
and arrangement of their floral whorls.

(1) Petaloideae. — All monocotyledonous plants with coloured
perianths (p. 187).

(2) Spadiciflorse.— All monocotyledonous plants with the
flowers enclosed in a spathe.

(3) Glumiflorae.— All monocotyledonous plants with the
flowers in glumes.

Each of these sub-classes into which the dicotyledons and
monocotyledons are divided includes a number of orders, and
each order consists of a number of familiar plants which are
closely related. The orders dealt with in this chapter are shown
below in a tabular form : —

Sub- Kingdom . . PHANEROGAMS.
Division .... ANGIOSPERMS.

Class DICOTYLEDONS.

Sub- Class .... Thalamiflorae.

Natural Order.

Distinguishing Characteristics.

(a) Ranunculaceae

(b) Cruciferse .

(i) Stamens indefinite (p. 188), hypogynous.
p. 185).
(ii) Pistil apocarpous (p. 186).

(i) Sepals and petals in the form of a cross,
(ii) Stamens 6, tetradynamous (p. 185).
(iii) Pistil, syncarpous (p. 186), carpels 2.

(i) Leaves, opposite and entire ; nodes swollen,
(ii) Stamens 10, in two series,
(iii) Pistil syncarpous.

R 2

244

BOTANY FOR BEGINNERS

CHAP.

Sub- Class .... Calyciflorae.

Natural Order.

(a) Leguminosae

Rosacese .

Distinguishing Characteristics.

(i) Flowers zygomorphic (p. 179).
(ii) Stamens 10, either monadelphous or dia-
delphous (p. 185).

(iii) Pistil monocarpous (p. 186).

(i) Flowers actinomorphic (p. 179).

(ii) Stamens indefinite, perigynous (p. 185).

(iii) Pistil apocarpous (p. 186) or monocarpous.

(i) Flowers in compound umbels (p. 168).
(ii) Stamens 5, epigynous (p. 185).
(iii) Pistil.

Sub- Class .... Gamopetalae.
Natural Order. Distinguishing Characteristics.

(a) Compositae. . .

(b] Primulaceae .

(c ) Boraginese .

(d) Scrophularineae.

(e) Labiatse . .

(i) Flowers in heads,
(ii) Stamens 5, syngenesious (p. 185).
(iii) Pistil syncarpous, carpels 2 ; ovary one-
celled, and stigma 2-fid.

(i) Flowers actinomorphic.

(ii) Stamens 5, opposite to corolla lobes.

(iii) Pistils syncarpous, carpels 5.

(iv. ) Placentation, free central (p. 187).

(i) Leaves entire and hairy,
(ii) Flowers rotate and actinomorphic.
(iii) Stamens 5, alternating with corolla lobes,
(iv) Pistil syncarpous, carpels 2 ; ovary four-
celled, style gynobasic (p. 186).

(i) Stem round,
(ii) Flowers zygomorphic.
(iii) Stamens 4, didynamous (p. 185).
(iv) Pistil syncarpous, carpels 2 ; ovary two-
celled, ovules numerous, axile placentation (p. 187).

(i) Stem square, leaves opposite,
(ii) Flowers two-lipped, zygomorphic.
(iii) Stamens 4, didynamous.
(iv) Pistil syncarpous, carpels 2 ; ovary four-
Jobed and four-celled, with one ovule in each cell.

xix THE CLASSIFICATION OF PLANTS 245

Sub-Class .... Incomplete.
Natural Order. Distinguishing Characteristics.

(a) Cupuliferae

(i) Male flowers in catkins,
(ii) Female flowers sessile in an involucre of
bracts.

Sub-Kingdom . . PHANEROGAMS.
Division .... ANGIOSPERMS.

Class MONOCOTYLEDONS.

Sub-Class .... Petaloideae.

Natural Order. Distinguishing Characteristics.

(a) Liliacese ... (i) Perianth either gamophyllous or poly-

phyllous.

(ii) Ovary superior ; ovules axile placentation.

(b) Amaryllideae . . ! (i) Perianth generally with a corona (p. 281).

I (ii) Ovary inferior.

Meaning of a Natural Order.— A natural order is built
up of a number of genera, each possessing some common charac-
ters. The genus in its turn includes several plants resembling
each other in one or more respects. The narrowest systematic
conception is the species. A species includes plants so closely
related that they must have descended from a common an-
cestor.

Naming of Plants.— Each plant receives two scientific
names ; the first indicates the genus, the second the species.
Thus, for instance, the Tormentil, Potentilla tormentilla, and
the silver-weed, Potentilla anserina, are two species of the
genus Potentilla.

The following scheme indicates how each plant is arranged
in its true position in the natural system of classification ;

Sub-Kingdom . . PHANEROGAMS.

Division ANGIOSPERMS.

Clans DICOTYLEDONS.

Sub-Class ... Calyciflorse.
Natural Order . . Rosaceae.

Genus Potentilla.

Species Tormentilla or Anserina.

246

BOTANY FOR BEGINNERS

CHAP.

DESCRIPTION OF NATURAL ORDERS.

Sub-Kingdom ,
Division . .
Class . . .
Sub- Class .

PHANEROGAMS.
ANGIOSPERMS.
DICOTYLEDONS.
Thalamiflorae.

Natural Order ; Ranunculaceae (Buttercup Family). —
The plants belonging to this natural order are usually medium-
sized herbs. The leaves are radical or cauline ; if the latter they
are alternate. The flowers are showy and actinomorphic. The
stamens are indefinite and hypogynous. The pistil is apocarpous.
The fruits consist of one-seeded achenes (p. 228), or many
seeded follicles (p. 230).

Floral formula. — K 5, C 5, A oo, G i to oo.

Description of a Typical Buttercup (Ranunculus
Acris],

Habit. — A hairy perennial plant with erect stem and straight
rootstock. It grows in meadows, and flowers from April to
September.

FIG. 237. — Hypogynous flower of Ranunculus, with numerous superior carpels on
the receptacle. (Magnified.) (S.)

Root. — A branched tap-root.

Stem. — Herbaceous, erect, round, hollow, hairy, green.

Leaves. — Both radical and cauline ; cauline leaves alternate,
simple ; lower leaves deeply divided ; upper, narrow and not
divided ; a well developed sheath present, reticulate-veined,
hairy, exstipulate.

Inflorescence. — Definite ; the axis ends in a flower.

Flower. — Complete, actinomorphic, about three quarters of
an inch in diameter, yellow.

XIX

THE CLASSIFICATION OF PLANTS

247

Calyx. — Polysepalous 5, inferior, hairy, green.

Corolla. — Polypetalous 5, hypogynous, each petal with a
nectary at base.

Andrcerium. — Free, indefinite, hypogynous ; filament long ;
anther two-lobed and basifixed.

FIG. 238. — Buttercup (Ranunculus). A, branch with flowers : B, longitudinal sec-
tion of flower ; C, flower from above ; D, flower from below ; E, petal ; F,
stamen ; Ca, carpel. (One-third nat. size.)

Gynacium. — Apocarpous ; carpels numerous, spirally arranged
on a conical receptacle ; superior.

Fruits. — Achenes with a single seed in each ; seeds possess
endosperm.

Pollination. — The outer stamens ripen first, then the inner
ones. The carpels ripen between the two sets of stamens. In
this way either self-pollination or cross-pollination can take
place. The flowers are visited by crowds of insects for honey
and pollen, and these, creeping over the flowers, may either
bring pollen from another flower, and so cross-pollinate ; or

248

BOTANY FOR BEGINNERS

CHAP.

they may distribute the pollen from the stamens to the pistil
of the same flower and produce self-pollination.

EXCEPTIONS TO THE ABOVE TYPE.

Monkshood (Aconitum napellus}. — Flowers \\\ racemes, zygomorphic ;
Calyx blue, sepals 5, the posterior one hood-like; Petals 8, 2 are
modified to form long-clawed nectaries ; the other 6 may be absent or

very minute ; Carpels 3 ;
ovules numerous. Protan-
drous ; Fruits of many-
seeded follicles ; Pollina-
ted by humble-bees.

Hellebore (ffelleborus).
—Sepals petaloid; Petals
8 to IO, minute and tubu-
lar, modified to form nec-
taries ; Protogynous ; Pol-
linated by insects ; H.
Niger is the Christmas
Rose.

Anemone (Anemone ne-
tnorosa], — Involucre of 3
bracts ; Sepals (petaloid)
white or purple ; Petals
absent ; Pollinated by in-
sects, wind, or self.

Traveller's Joy (Clema-
tis vitalba}. — Slem woody, leaves opposite ; Sepals 4 to 6, white ;
Petals absent ; Pollinated by insects.

Larkspur (Delphinium). — Sepals 5, either separating or cohering
below ; one is spurred ; Petals small.

Marsh Marigold (Caltha palustris}. — Grows in marshes and wet
ditches ; Sepals 5, large and yellow ; Petals absent.

Columbine (Aqttilegia vulgaris}. — Flowers purple and solitary or in
panicles ; Sepals 5, petaloid and regular ; Petals 5, spurred ; Prot-
androus ; Pollinated by insects.

Properties of Eanunculaceae. — The plants of this order are very rich
in substances that possess poisonous properties. The most poisonous
plants are Aconitum (all species). The root of this genus has
been mistaken for the Horse-radish. It can be distinguished by the
following characters : — •

FIG. 239. — i, Flower of Monkshood ; 2, stamens
nectaries, and pistil. (S.)

Aconitum.

The rootstock is from two to
three inches in length, and ends
in a point.

It is coffee coloured, and pos-
sesses no pungent smell.

If scraped when fresh it turns
pink.

Horse-radish.

The rhizome is from three to
four times as long as the root of
Aconitum.

It is of a light yellow colour,
and possesses a pungent smell.

It does not turn pink when
scraped.

The root of Aconitum is largely used in medicine.

XIX

THE CLASSIFICATION OF PLANTS

249

Ranunculus. — All species are more or less poisonous. The Celery -
leaved Crowfoot is probably most poisonous. K. acris frequently
causes poisoning in cattle. The Marsh Marigold is a source of danger
to children, who are attracted by its large yellow flowers.

All species of Anemone and Helleborus are poisonous.

FIG. 240. — Monkshood (Aconitum). (One-third nat.
size). (S.)

FIG. 241. — Floral
diagram of Cruciferae.

Natural Order : Cruciferae.— (Wallflower Family). The
plants of this order have either radical or cauline leaves, which
are exstipulate. The flowers are in racemes and are cruciform.
Sepals 2 + 2, the two lateral ones saccate. Petals 4, Stamens
6, tetradynamous. Pistil syncarpous, carpels 2. Ovary two-
celled. Ovules numerous, parietal placentation. Fruit either
a siliqua or silicula.

NOTE. — This is the only order with tetradynamous stamens.

Floral formula.— -K2 + 2, C4, A2 + 4,6(2).

BOTANY FOR BEGINNERS

CHAP.

Description of a typical Crucifer. Cheiranthus
Cheiri. — (Wallflower).

Habit. — A perennial plant which grows on old walls, and is
largely cultivated in gardens.

Root. — A much branched, woody tap-root.

FIG. 242. — Wallflower (Cheiranthus). A, Branch and inflorescence ; B, flower ;
C, longitudinal section of flower ; D. stamens and pistil : E, fruit ; S, transverse
section of stem. (One-fourth nat. size.)

Stem. — Woody below and herbaceous above, erect, branched,
ribbed ; the lower part is covered with pale brown bark, and
the upper portion is coloured green and is hairy.

Leaves. — Cauline, alternate, sessile, lanceolate, acute, entire
and reticulate-veined. Upper side dark green and slightly
hairy ; the lower side pale green and more hairy ; exstipulate.

XIX

THE CLASSIFICATION OF PLANTS

Inflorescence.. — Indefinite, erect, raceme.

Flowers. — Complete, actinomorphic, cruciform. Diameter i^
inches. Yellow or reddish-brown in colour and sweet scented.

Calyx. — Polysepalous 2 + 2, inferior ; inner sepals saccate ;
sepals lanceolate and hairy.

Corolla. — Polypetalous ; petals 4, hypogynous and clawed.

Androzrium. — Free ; stamens 6, tetradynamous, hypogynous;
filaments thick, anther two-lobed.

Gyncecium. — Syncarpous ; carpels 2 ; ovary superior, linear,
spuriously two-celled ; style short ; stigma 2-fid.

Ovules. — Numerous, parietal placentation.

Fruit. — A siliqua. Seeds with a little endosperm.

Pollination. — The flowers are visited by insects for their
honey, which is stored in the saccate sepals.

FIG. 243.— Wild Radish (Raphanus Sativus.. «, flower (nat. size) ; b, petal ; c, an-
droecium and gynoecium ; d, pistil with glands ; e, fruit ; f, transverse section
of fruit ; g and A, embryo. (S.)

Properties of Cruciferae. — All Crucifera are wholesome, being
largely used for food. Many are valuable because of the organic acids
they contain.

The principal plants of this order cultivated for food are : (a) For
their roots, Turnip (Brassica campestris}. (b) For their leaves, Cabbage
(Brassica). " Brussels-Sprouts " is a variety of Cabbage which produces
large axillary buds. The young seedlings of the Cress (Leptdium sat-

252

BOTANY FOR BEGINNERS

CHAP.

ivum\ and the White Mustard (B. alba) are used for salads, (c) For
their inflorescences — Cauliflower and Broccoli are varieties of Cabbage.
Their inflorescences are branched and very succulent. The flowers are
very minute, (d] For their seeds, Black Mustard (B. nigra), from
which the mustard of commerce is produced, (e) For their oil, Rape
and Colza (varieties of Brassica}. The oil is obtained from their seeds.

Natural Order: Carophyllese, (Stitchwort family).—
The plants belonging to this order have swollen nodes, opposite
leaves which are entire and narrow. The flowers are solitary or in
dichotomous cymes. The calyx consists of five united or free
sepals. The corolla is made up of five petals, each deeply cut
or entire. There are 10 stamens in two series which ripen five
at a time. The pistil is syncarpous, the
carpels varying in number from 3 to 5.
The placentation of the ovules is axile.
Fruit is a capsule. The flowers are pro-
tandrous and pollinated by insects.

NOTE. — No other order possesses the
combined characters of swollen nodes, oppo-
site entire leaves, and 10 free stamens in two
series.

Floral formula.— K$,C5,A$ + 5,6(2 to 5)
Description of a typical Caryo-
phyllaceous Plant (Stellaria media).—
$titchwort.

Habit. — An annual herbaceous plant with many branches,
which grows nearly everywhere.
Root. — Short, and very slender.

Stem. — Swollen at the nodes, very hairy, herbaceous and
green.

Leaves. — Cauline, opposite, simple, entire, narrow. Lower
leaves possess petioles, while the upper are sessile ; exstipulate.
Inflorescence. — Definite, forming dichotomous cymes.
Flowers. — Complete, actinomorphic, stellate, small, white.
Calyx. — Polysepalous ; 5 inferior green sepals.
Corolla. — Polypetalous ; 5, hypogynous, petals split.
Andrcecium. — Free ; 10 stamens in two series ; hypogynous ;
the outer whorl of stamens is opposite the petals, and the others
alternate with them ; filament slender ; anther two-lobed.

Gyncecium. — Syncarpous ; carpels 3 ; superior ; styles 3 ;
stigmas 3.

FIG. 244.— Floral
diagram.

XIX

THE CLASSIFICATION OF PLANTS

253

Ovary. — One-celled ; ovules axile placentation.

Fruits. — A capsule which opens by valves. Seeds with
perisperm.

Pollination. — Honey is produced in five nectaries, forming
small knobs outside the stamens. The flowers are cross-pol-

FIG. 245. — Stitchwort (Stellaria). A, branch, with inflorescence; B, longitudinal
section of flower ; C, corolla, as seen from above ; D, petal ; E, stamen ; F,
pistil. (One-fourth nat. size.)

linated by insects. Some of the flowers never open and are
self-pollinated. These are not cleistogamic.

NOTE. — This plant is most variable. In some cases the
sepals may be 6. The stamens opposite the petals may be
absent, and in a few cases all the stamens may be wanting.
The flowers of the Pink, Catchfly, and Campion have the calyx
gamosepalous and the petals are clawed.

Properties. — A few plants of this order possess poisonous properties.
The most dangerous plants are : — Lychnis githago^ the Corn Cockle,
which grows in cornfields. Its leaves are very narrow, flowers violet-

254

BOTANY FOR BEGINNERS

CHAP.

coloured, and the seeds are produced in capsules. It is harvested along
with the corn, and is separated from it by machinery. If the flour
should contain large quantities of the seeds of this plant bad results may
follow from its use. Saponaria officinalis, the common soap-wort, is a
stout perennial plant with rose-coloured flowers. All parts of this
plant possess a poisonous substance.

FIG. 246. — A, branch of Campion ; B, a separate flower ; C, longitudinal section of
flower ; D, flower seen from above.

Sub-Class. Calyciflorae.

Natural Order : Leguminosse (Pea Family).— The plants
belonging to this natural order may be either herbs, shrubs, or
trees. The leaves are alternate, being usually compound and stipu-
late. The flowers are zygomorphic and papilionaceous. The calyx

XIX

THE CLASSIFICATION OF PLANTS

255

is gamosepalous. The corolla is polypetalous and consists of a
standard, wings, and keel The 10 stamens are either dia-
delphous or monadelphous. The pistil is monocarpous. The
fruit is a legume while the seeds are exalbuminous.

Floral formula.— K(5), €5, A(Q) + I or (10), G£.

Description of a typical plant of the Leguminosse.—
(Pisum Sativum, Garden Pea). -

FIG. 247. — A, leaf and flower of Pea ; B, a side view of flower ; C, flower from
above ; D, longitudinal section of flower ; i, standard ; 2, 2', wings ; 3, the two
petals which form the keel.

Habit. — A weak annual plant which climbs by means of
tendrils.

256 BOTANY FOR BEGINNERS CHAP.

Root. — A branched tap-root with a large number of nodules on
the branches. These nodules are caused by bacteria (p. 132).

Stem. — Herbaceous, ribbed, solid, hairy, green.

Leaves. — Cauline, alternate, pinnately compound, stipulate ;
the stipules are large, green, and persist ; some of the leaflets
are converted into tendrils.

Inflorescence. — Axillary and two flowered.

Flower. — Complete, zygomorphic, papilionaceous ; diameter
one inch ; generally white in colour.

Calyx. — Gamosepalous ; 5 lobed ; perigynous ; green and
hairy.

Corolla. — Polypetalous ; 5 petals ; perigynous ; consists of a
standard, wings, and a keel. (p. 180).

Andrcecium. — Diadelphous ; 9+1 stamens ; perigynous ; the
single posterior stamen is free and the rest are united, having an
opening all along the posterior face as well as at the top of the
bundle. At the base of the inner row of stamens five nec-
taries occur. The honey formed by them accumulates between
the stamens and the base of the ovary.

Gynoecium. — Monocarpous ; superior ; parietal placentation.

Fruit. — A legume ; seeds exalbuminous.

Pollination. —The flowers of all the plants of this order are
adapted for insect pollination. The pea is generally pollinated
by the bee. The insect rests on the flower using the wings of
the flower as a platform ; its weight pulls these down and draws
the keel forward. The stamens, protected by the keel, thus come
in contact with the under side of the bee and dust it with pollen,
The bee now thrusts its tongue down the slit in the bundle of
stamens and sucks up the honey. As flower after flower is
visited, cross-pollination occurs. Self-pollination sometimes
takes place.

Other Leguminous Plants. — Trifolium repens (Dutch Clover) is a
creeping perennial. Each leaf is divided into three leaflets and at its
base there is a pair of small stipules. The flowers are in heads.

Cytisus (Laburnum and Broom) possesses monadelphous stamens.

Viciafaba (Broad Bean) possesses a strong erect stem.

Phaseolus coccineus (Scarlet Runner) has a left-handed twinging stem
by means of which it climbs around slender supports.

Properties of Leguminosae. — Many are largely used in medicine ;
some are poisonous, others are largely cultivated for food.

Laburnum. — The seeds of Laburnum are poisonous. The plant can

XIX

THE CLASSIFICATION OF PLANTS

257

be recognised by its ternate leaves, its racemes of large yellow flowers,
and many seeded legumes. Most of the other plants belonging to the
genus Cytisus are poisonous.

Leguminous Plants Cultivated for Food. — The following are the
principal plants which are cultivated for food in the United Kingdom :—

Garden Peas — Pisum.
Beans — Phaseolus.
Clovers — Trifolium.
M edick — Medicago.
Sainfoin — Onobrychis.

Vetches or Tares — Vicia.
Bird'sfoot Trefoil — Lottts.
Kidney- Vetch— Anthyllis
Common Melilot — M. officinalis.
Furze, gorse, or whin — Ulex.

•

FIG. 248. — Bird's-foot Trefoil (Lotus corniculatus.) i, Flowering branch ; 2, flower ;
3, pistil and stamens : 4, carpel ; 5, fruit ; 6, corolla ; a, standard ; b, wings ; c,
keel ; 7, floral diagram.

Natural Order : Rosacese (Rose Family).— The plants of
this order are either herbs or woody plants. The leaves are
generally alternate and stipulate. The flowers are actinomor-
phic and perigynous. The sepals and petals are usually four or
five in number and the stamens are indefinite and perigynous.
The pistil is either apocarpous or monocarpous while the number

258

BOTANY FOR BEGINNERS

CHAP.

of carpels varies from one to many. Fruit various. Seeds
either with or without endosperm.

NOTE. — The difference between the plants of this order and
those of the natural order Ranunculaceae consists in their perigy-
nous stamens.

FIG. 249.— Blackberry (Rubus fruticosus). i, Flowering branch ; 2, longitudinal
section of flower ; 3, fruit ; 4, floral diagram. (S.)

Floral formula.— K(s), €5, Aco , G i to w.
Description of a typical plant of Rosacese (Rosa
camna, Dog Rose).—

Habit.— A prickly shrub with large coloured flowers.
Root. — A tap-root with woody branches.
Stem.— Woody, prickly, and covered with bark.

XIX

THE CLASSIFICATION OF PLANTS

259

Leaves. — Cauline, alternate, pinnately compound, with a
terminal leaflet. The margin of the leaf is serrate. Leaves are
stipulate, and these are adnate (p. 46).

Inflorescence. — Definite. The flower is produced at the end
of a branch (in some cases other flowers may be produced in
subjacent bracts).

Bract. — Bracteate.

Flower. — Complete, actinomorphic, large, coloured, and sweet-
scented.

FIG. 250. — Pear (Pyrus communis). r, Flowering branch ; 2, longitudinal section of
flower : 3, longitudinal section of fruit ; 4, floral diagram. (S.)

Calyx. — Gamosepalous, 5 lobed, sepals inferior.
Corolla — Polypetalous ; 5 perigynous petals.
Androecium. — Free, indefinite, perigynous stamens.
Gynoecium. — Apocarpous ; carpels numerous and superior.
Each carpel contains a single ovule.

S 2

200

BOTANV FOR BEGINNERS

CHAP.

Fruit. — A pseudocarp concealing a number of achenes.
have no endosperm.

Pollination. — By insects.

Seeds

EXCEPTIONS TO THE ABOVE TYPE.

The order Rosaceae is a very large one, and contains a number of
plants differing in some respects from the Dog Rose.

Strawberry (Fragaria vesca) —

Calyx. — Under the calyx, and alternating with the sepal, a whorl 01
sepal-like members is developed. This whorl forms an epicalyx, repre-
senting the stipules of the sepals joined together.

Fruit. — The fruit is formed by the enlargement of the receptacle,
which swells after pollination, becoming at first white, then red, sweet,
and juicy.

Blackberry and Raspberry (Rtibus}—-

Fruit. — The carpels enlarge after fertilisation, become succulent, and
form one-seeded druplets. The fruit is compound and inserted on a
receptacle bearing the persistent calyx.

FIG. 251. — Cherry (Prunus cerasus). i, Flowering branch ; 2, longitudinal section of
flower; 3, longitudinal section of fruit. (S.)

Cherry, Plum and Apricot (Prunus) —

Pistil. — The pistil is monocarpous ; after pollination the single carpel
swells up and a one-seeded fruit is produced. This is a drupe which is
a simple fruit.

XIX

THE CLASSIFICATION OF PLANTS

261

Apple and Pear (Pyrtis) —

Pistil. — The pistil consists of five carpels which are united to one
another along their sides. In the Apple the five styles are united at
their base, but in the Pear they are free.

FIG. 252. — A, Twig of Apple ; B, longitudinal section of flower ; C, flower, with
corolla absent ; D, view of flower from below ; E, a single stamen ; F, pistil,
with portion of calyx. (One-fourth nat. size.) Ca, calyx ; p, petal ; st, stamens ;
s, style ; o, ovary.

Fruit. — After pollination the calyx tube which surrounds the pistil
swells up and produces an inferior fruit known as a pome.

Hawthorn (Cratcegus] —

Pistil. — The pistil differs from that of the Apple in consisting of only
two carpels and in being two-celled.

Fruit. — The portion of the receptacle surrounding the carpels
becomes hard and forms a stony endocarp. Thus, the fruit is a stone-
fruit with two stones.

Ladies' Mantle (Alcheinilla)—1\& stamens are definite, and the
anthers are one-celled.

262 BOTANY FOR BEGINNERS CHAP.

Properties of Rosaceae. — The seeds of many species contain prussic
acid in small quantities. The Cherry Laurel contains this acid in the
leaves, and if these are eaten they produce intoxication. A very large
number of the plants of this order are used in medicine.

Rosacese Cultivated for their Fruits.

Apple and Pear — Pyrus.

Almond, Peach and Nectarine — Amygdahis.

Cherry, Apricot and Plum — Prunus.

Strawberry— /'Vrt^a/Ya.

Raspberry and Blackberry — R-ubus.

Natural Order: Umbelliferse (Parsley Family).— All
the plants of this order are herbs with alternate leaves,
„ generally compound. The inflorescence is

usually a compound umbel, and an involucre
of whorled bracts. The flowers are small
and actinomorphic. The calyx is gamo-
sepalous, 5 lobed and superior. The corolla
is polypetalous, there being 5 epigynous
petals (p. 184). The 5 stamens are epigy-
nous. The pistil consists of 2 carpels, 2
styles, and I ovule in each cell of the ovary.

* IG. 253. — Floral _, r . . . . , ON

Diagram. The fruit is a schizocarp (p. 228).

Floral formula.— K(5),C5,A5,G(i).

Description of a typical plant of the Umbelliferee
(Heradeum Sphondylium, Cow Parsley).

Habit. — A coarse hairy plant with small white flowers in
compound umbels.

Root. — A tap-root with numerous branches.

Stem. — Herbaceous, erect, hollow, ribbed, hairy, and green.

Leaves.— Cauline, alternate, deeply divided, with large sheaths
which clasp the stem ; exstipulate.

Inflorescence. — Indefinite, compound umbels.

Bracts. — Bracteate, forming an involucre at the base of the
main umbel, and partial involucres at the base of the secondary
umbels.

Flower. — Complete, actinomorphic, small, white or yellow ;
the outer flowers may be zygomorphic.

Calyx.— Gamosepalous, 5 lobed, superior, green and hairy.

Corolla.— Polypetalous, 5, epigynous.

XIX

THE CLASSIFICATION OF PLANTS

263

Androsdum. — Free, 5, epigynous, alternating with the
petals.

Gynoscium. — Syncarpous, carpels 2, inferior, ovary two-celled,
with one ovule in each cell.

Fruit. — The fruit is a schizocarp which splits into two meri-
carps. Seeds with endosperm.

FIG. 254. — Water-Parsnip (Sium latifolium). (Half nat. size.) (S.)

Pollination. — The flowers are small and crowded together.
Honey is produced by an enlarged disc, the nectary. The
honey being freely exposed, the flowers are visited by short-
tongued insects, which cross-pollinate the flowers. The principal
insects which visit the flowers are flies, beetles, and wasps.

264 BOTANY FOR BEGINNERS CHAP, xix

Properties of Umbelliferae. — Many are noted for their poisonous
properties. Some are very dangerous in the wild state but harmless
when cultivated. Thus, wild Celery is poisonous, but when blanched
by being deprived of light the poisonous matter is not produced ;
light seems to be necessary for its production. The principal poisonous
plants of this order are : —

Poison Hemlock (Conitim maculatuni}. — A glabrous herb, often
more than a yard high, with hollow stems. The lower portion of the
stem is often spotted with purple. If the plant is bruised it emits a
disagreeable odour which resembles mice. Hemlock was the State
poison of Athens and by it Socrates met his death.

The Water Hemlock (Cicttta virosa). — This plant grows along the
sides of ponds and ditches, and is the most dangerous of all poisonous
plants. The stem is an underground rhizome which contains internal
cavities. The leaves are large and tripinnate, and the narrow and
lanceolate leaflets are also tripinnate.

The Fool's Parsley (Aethusa cynapiuni). — This plant differs from
true Parsley in having white instead of yellow flowers. It often grows
as a weed in gardens, and emits an odour of garlic. When it is eaten
it produces intoxication.

The Water Drop-wort (CEnanthe crocata}. — This plant grows along
the edges of ditches and marshes, and flowers in July. It is very much
like Celery, and is often mistaken for it. The root fibres are about as
thick as the thumb, and the juice is either yellow or colourless. The
stem is from two to three feet high, thick, branched, and grooved. The
petioles sheath the stem throughout.

Useful Species of Umbelliferae. — Many of the Umbelliferae are
useful. Among useful members may be mentioned : —

Carrot. Parsley.

Parsnip.
Celery.

Caraway.
Coriander.

Fennel.
[For Summary and Questions, see end of next chapter}.

CHAPTER XX

CLASSIFICATION OF PLANTS (Continued}

Sub-class : — Gamopetalae.

Natural Order : Compositae (Composite Family).—
The plants of this order which belong to the British flora are
herbs. Their leaves are various and ex- •

stipulate. Flowers small and occur in
heads. The calyx is small or absent ; in
some cases it is replaced by a pappus of
hairs. The corolla consists of from 3 to 5
petals. The 5 stamens are syngenesious
(p. 185), and epipetalous. The pistil is syn-
carpous, carpels 2, inferior. The ovary is
one-celled with a single ovule. Seeds ex-

FIG. 255. — Floral

albuminous.

Floral formula.— K($ - o)C(5,)A(s),G(2).

Division of Compositse.— The plants of this order are
divided into two sub-orders : (a) Tubuliflorce — with the flowers
actinomorphic, or the ray florets one -lipped, e.g., Daisy,
Thistle. (£.) Liguliflorce — with the flowers ligulate or strap-
shaped, e.g., Dandelion, Hawk's-weed.

Description of a Typical member of Tubuliflorae
(Bellis perennis, Daisy). —

Habit. — A perennial herbaceous plant, growing in meadows.

Stem. — An underground rootstock.

Leaves. — Radical, petiolate, toothed, green.

Inflorescence. — Indefinite, head or capitulum (p. 168).

Flowers. — The central flowers are termed disc flowers* and

266 BOTANY FOR BEGINNERS CHAP.

those on the outside, ray flowers. The disc flowers are
incomplete but perfect (p. 178), actinomorphic, tubular, and
minute. The ray flowers are incomplete, imperfect, zygomorphic,
ligulate, and minute.

Calyx. — Absent in both disc- and ray-flowers.

Corolla. — Thedfof- flowers are gamopetalous, 5 lobed,epigynous.

The nzy-flowers are gamopetalous, 3 lobed (may consist of
five petals), epigynous.

Andrcecium. — The dEw-flowers — stamens, syngenesious, 5,
epipetalous.

The ray-flower, stamens absent.

Gyncecium. — In both ray- and dw-flowers — Syncarpous,
carpels 2, inferior, style 2-fid.

Pollination. — The disc-flowers are protandrous. The pollen
from them accumulates in the tube formed by the united
anthers. The style branches possess hairs on their outer
surfaces and these, when the style pushes its way up the tube,
act like a paint brush and sweep the pollen out. The insects
are attracted to the head by the ray-flowers, which make the
head very conspicuous. The insects creeping over the surface of
the inflorescence carry pollen from inflorescence to inflor-
escence, and cross-pollination takes place. If not pollinated
in this way, the style turns down and touches the pollen, and
self-pollination takes place.

Description of a typical member of • Liguliflorse.
( Taraxacum Dens-leonis, Dandelion.)

Habit. — A perennial herb which contains a milky fluid ;
radical leaves, and a hollow radical peduncle, carrying a head of
bright yellow flowers.

Stem. — A short tap-root, is capped with a short erect
rhizome.

Leaves. — Radical, simple, runcinate.

Inflorescence. — Indefinite, head of from 100 to 200 flowers.

Bracts. — The Bracts form an involucre.

Flower. — Complete, zygomorphic, ligulate, small, yellow.

Calyx. — Represented by a pappus of hairs.

Corolla. — Gamopetalous, 5 lobed, epigynous.

Androecium. — Syngenesious, 5, epipetalous.

Gynoecium. — Syncarpous, carpels 2, inferior, style 2, stigma

2-fid.

xx THE CLASSIFICATION OF PLANTS 267

Fruit. — The fruit is a one-sided indehiscent achene and
carries a pappus of hairs, which is a modified calyx.

Pollination. — The description of the pollination of the Daisy
holds good for the Dandelion.

FIG. 256.— Dandelion (T. Dens-leonis). i, Two inflorescences and a leaf; 2, a
flower ; 3, fruit ; 4, receptacle, with one fruit. (S.)

Properties of Compositae. — Many are used in medicine, and a few
only are poisonous. Lactuca virosa> the Lettuce, contains an ill-
smelling latex which is slightly poisonous.

Further remarks on the Compositae. — This order is the largest in
the vegetable kingdom, and the best defined of all the natural orders.
There are some 12,000 species, all agreeing in having their flowers in
heads and their stamens syngenesious. A few plants of this order are

268

BOTANY FOR BEGINNERS

CHAP.

cultivated either for food or for ornamental purposes. The following
are of service to man : —

Sunflower (Helianthus annuus\ cultivated for its seeds, which yield
a valuable oil.

Jerusalem Artichoke (H. tuberosus\ cultivated for its tubers. It only
flowers in the United Kingdom during very hot summers.

Garden Chrysanthemum (Chrysanthenmtn indicum}, cultivated for
its beautiful flowers.

Chicory (Cichorium intybus], useful for its roots, which are dried in
kilns, roasted, ground, and mixed with coffee.

Lettuce (Lactuca). — Its leaves are used for salad.

Other Composite which are Cultivated in Gardens.

Cineraria. Chamomiles.

Helichrysum. Daisy.

Gaillardia. Dahlia.

Calliopsis. Senecio.

Natural Order: Primulaceee (Primrose Family).— The
plants of this order are herbs with radical leaves. The flowers
» are actinomorphic and showy. The calyx

is gamosepalous, 5 lobed, and inferior. The
corolla consists of 5 petals, which are gamo-
sepalous and hypogynous. The five stamens
face the lobes of the corolla, and are epi-
petalous. The pistil is syncarpous, has five
carpels, and is superior. The ovules are
numerous, and free central placentation oc-
curs. The style is simple, and stigma capi-
tate. The fruit is a capsule.

Floral formula.-\^\ [C(5),As,]G(5).
Description of a Typical Plant of Primulacese (Pri-
mula vulgaris, Primrose).

Habit. — A herbaceous perennial plant with radical leaves and
showy flowers.

Root. — Fibrous, forming a dense mass.
Stem. — A stout erect rhizome.

Leaves. — Radical, simple, spathulate, reticulate-veined; margin
crimped ; dark green above and light green below ; exstipulate.
Inflorescence. — Definite, solitary.

Flower. — Complete, actinomorphic, tubular ; i inch in dia-
meter ; dimorphic pale yellow, and sweet scented.

Calyx.— Gamosepalous, 5 lobed, inferior, apex of lobes acute,
ridged, green and hairy.

FIG. 257. — Floral
Diagram.

THE CLASSIFICATION OF PLANTS

269

Corolla. — Gamopetalous, 5 lobed, hypogynous, lobes divided.
Andr&aum.r—¥ittj 5, facing the lobes of corolla, epipetalous.
Gynaechem. — Syncarpous, carpels 5, superior, style long or
short, stigma capitate, ovules numerous, free central placentation.

Fig. 258.— Primrose (Primula). A, R adical leaves and flowers ; B, flower ; C,
long-styled flower ; C1, short-styled flower ; D, section of stem. (One-fifth nat.
size.)

Fruit. —A capsule. Seeds with endosperm.
Pollination. — Cross-pollinated by insects (p. 209-10). Self-
pollination is possible in the short-styled form.

Properties of Primulaceae. — The properties of the plants of this order
are unimportant. The tubers of Cyclamen are poisonous, but after
cooking they are perfectly harmless.

270 BOTANY FOR BEGINNERS CHAP.

Natural Order : Boraginese (Borage Family).— The
plants can be easily recognised by their succulent stems covered
with hairs, their entire leaves and scor-
pioid cymes. The flowers are generally
blue and actinomorphic. The calyx is
gamosepalous, 5 lobed, inferior. The
corolla is gamopetalous, 5 lobed, and
hypogynous. The five stamens are
epipetalous and alternate with the lobes
"Sfcss..^^-— *&* of corolla. The pistil is syncarpous,

carpels 2, superior. Each carpel is 2
FIG. 259.— Floral diagram, lobed, thus forming a 4 lobed ovary.
The style is gynobasic (p. 186). The
fruit consists of four indehiscent nutlets.
Floral formula.- -K(s), [C(s), AS] 6(2).
Description of a Typical Member of Boraginese
(Myosotis palustris, Forget-Me-Not).

Habit. — A perennial herb with entire leaves, and bright blue
flowers.

Root.— Rootstock creeping.

Stem. — A creeping stolon with small leaves. The aerial stem
is from i to 2 feet high; herbaceous, erect, ribbed, hollow,
hairy, green.

Leaves. — Cauline, alternate, sessile, simple, entire, hairy,
green.

Inflorescence. — Definite, scorpioid cyme.

Flower. — Complete, actinomorphic, rotate, minute, blue, throat
of corolla closed with fine scales.

Calyx. — Gamosepalous, 5 lobed, inferior, green, hairy.
Corolla. — Gamopetalous, 5 lobed, hypogynous.
Andrcecium. — Free, 5 stamens, epipetalous, alternating with
lobes of corolla, filament short.

Gyncecium. — Syncarpous, 2 carpels, superior ovary, 4 lobed,
style gynobasic, stigma capitate.
Fruit. — Four indehiscent nutlets.
Pollination.— By insects.

Properties of Boraginese. — The properties of the plants of this
order are unimportant. The dried root of Alkanet, cultivated through-
out the south of Europe, is used in medicine.

THE CLASSIFICATION OF PLANTS

27 [

Other Boragineae which should be noticed.

Viper's Bugloss — Echhtm vulgare.
Borage — Borago officinalis.
Comfrey — Symphytwn officinale.
Cromwell — Lithospernmm officinalis.
Lungwort — Pubnonaria augustifolia.
Madwort — Asperugo procumbens.

FIG. 260. — Forget-me-not (Myosotis). A, branch, with inflorescence; B, flower;
C, corolla and scales from above ; D, section of stem ; E, longitudinal section of
flower. (Half nat. size.)

Natural Order : Scrophularinese (Foxglove Family).—
The plants of this order are herbs, with simple toothed leaves,
which as a rule are alternate. The inflorescence may be soli-
tary, axillary, or a raceme. The flower is zygomorphic, and
very often showy, The calyx is gamosepalous, 5 lobed, inferior.
The corolla is gamopetalous, 5 lobed, hypogynous. The stamens
are usually 4 (2 in Veronica), didynamous (p. 185), epipetalous.
The pistil is syncarpous, carpels 2, superior ; style terminal,

272

BOTANY FOR BEGINNERS

CHAP.

ovary two-celled, ovules axile placentation. The fruit is a
capsule.

Floral formula.— K($\ [C($\ A4]G(2), or K(4), [C (4),A2G](2).

Description of a Typical Plant of the Scrophula-
rinese. — {Digitalis purpurea, Foxglove).

Habit. — A tall perennial herb, which flowers from July to
September.

Stem. — Herbaceous, erect, round, green.

c ii e

\ (

out ; c, calyx and pistil ; J, fruit ; e, section of fruit,

FIG. 261. — Foxglove (Digitalis purpurea). a, Flower ; b, corolla cut open and spread

't, (S.)

Leaves. — Lower ones radical and stalked; upper ones cauline
and sessile.

Inflorescence. — Indefinite ; raceme.

Flower. — Complete, zygornorphic, tubular, large, purple, with
spots inside.

Calyx. — Gamosepalous, 5 lobed, inferior.

THE CLASSIFICATION OF PLANTS

273

Corolla. — Gamopetalous, 5 lobed, hypogynous ; the lower lip
of corolla is longer than the upper lip.

Andrascium. — Free, 4 stamens, didynamous, epipetalous, fila-
ments various, anthers 2 lobed.

Gyncecium. — Syncarpous, 2 carpels, superior, style terminal ;
stigma 2-fid ; ovary 2-celled ; ovules numerous : axile placenta-
tion.

Fruit. — A two-valved capsule.

Pollination. — The flower is protandrous, and is pollinated
by humble-bees, which creep into the flower and are dusted
with pollen on their backs.

EXCEPTIONS TO THE ABOVE TYPE.

Speedwell ( Veronica) — Leaves. — Opposite ; Inflorescence. — Either an
axillary or a terminal raceme ; Corolla. — Petals 4, lobes unequal ;

Stamens. — 2 only.

Mullein ( Verbas-
cuni ) — Stamens. — 5 •

Properties of
Scrophularineae. —
Several of the plants
of this order are
poisonous, and are
used in medicine.
The most poisonous
is the Foxglove, all
parts of which are
poisonous.
o

FIG. 262. — Speedwell (Veronica). A, flowering branch ;
B, flower ; C, flower, viewed from above ; D, petal ;
E, stamens ; F, section of flower.

FIG. 263.— Floral
diagram of
Speedwell."

Many of the plants are root -parasites, and are provided with suckers
which penetrate into the roots of the host plant, e.g., Yellow Rattle,
Cow-Wheat, Eye-bright, and Lousewort.

274

BOTANY FOR BEGINNERS

CHAP.

Natural Order : Labiatse (Labiate Family).— The plants
of this order can be recognised by their square stem and oppo-
site leaves. The inflorescence is a verticillaster (p. 173). Tho
flower is zygomorphic. The calyx is gamosepalous, 5 lobed,
and inferior. The corolla is gamopetalous, 5 lobed, hypogynous,
and two-lipped. The stamens (2 or 4) are epipetalous ; if four,
didynamous. The pistil is syncarpous, carpels 2, superior, style
gynobasic, ovary 4 lobed. The fruits consist of 4 nutlets.

NOTE. — The Labiatae can be distinguished from the Scrophu-
larineae by their square stem and opposite leaves, and by the
4 lobed ovary and gynobasic style ; from the Boragineae by
the stamens being fewer in number than the lobes of corolla,
and by the zygomorphic flowers.

Floral formula.— K(s\ [C(5), A4], G(s).

Description of a Typical Plant of the Labiatse
(Lamium album, White Deadnettle).

Habit. — A peren-
nial herb with
square stem and
coarse foliage.

Mem. — Herba-
ceous, erect, square,
hollow, hairy,
green.

FIG. 264. — Floral
diagram.

FIG. 265.— Deadnettle (Lamium). A, flowering branch ;
B, flower ; C, section of flower ; D, flower viewed from
the side ; S, section of stem. (One-sixth nat. size.)

Leaves.— Cauline, opposite, simple, cordate, serrate, hairy.
Inflorescence. — Definite ; verticillaster.

Flower. — Complete, zygomorphic, £ of an inch in diameter
labiate, white, faintly scented.

xx THE CLASSIFICATION OF PLANTS 275

Calyx. — Gamosepalous, 5 lobed, inferior, lobes acute, hairy
green.

Corolla. — Gamopetalous, 5 lobed, hypogynous, very hairy.

Andrceciuin. — Free, 4, didynamous, epipetalous, filament
round and hairy, anthers 2 lobed.

Gynceciiun. — Syncarpous, carpels 2, superior, style gynobasic ;
stigma 2-fid, ovary 4 lobed ; I ovule in each cell of ovary.

Fruit. — Four nutlets.

Pollination. — Pollinated by humble-bees, which creep into
the flower to suck the honey from the nectary. As the bee
creeps into the flower its back touches the stigma, and is after-
wards dusted with pollen from the anthers. Thus cross-pollina-
is effected.

Properties of Labiatae. — None of the plants of this order are poison-
ous, but many species possess essential oils which are formed by glands
in the tissues of the leaves. The oil can be separated by distillation.
Many of the plants of the order are used for cooking purposes, such as
Mint, Pennyroyal, Marjoram, Thyme, Sage, and Balm.

Sub-Class : Incompletse.

Natural Order : Cupuliferae (Oak Family).— The plants
of this order include most of. the shrubs and trees found in the
temperate regions of the globe. The leaves are simple, monoe-
cious (p. 208). The male inflorescence is generally a catkin.
The flowers are small and inconspicuous. The perianth is
either absent or small and green, The stamens vary in number
from 4 to 6, The pistil is syncarpous, carpels from 2 to 6, ovary
either 2 or 3 celled, with i or 3 ovules in each, The fruit is
often i -seeded, indehiscent — a nut. Many plants of this order
possess a cupule. Seeds are without endosperm.

Description of a typical Member of the Cupuli-
ferse. — (Corylus Avellana, Hazel).

Habit. — A deciduous shrub, with monoecious flowers ; the
main stem breaks up into branches just above the ground.

Root. — The primary root of the seedling grows only for a
short time, then gives off several lateral roots which run along
just beneath the surface soil in a horizontal manner.

Stem. — The base of the stem beneath the ground gives off
suckers (p. 21) which grow upwards, and from their lower side
adventitious roots are produced. If from any reason the

T 2

276

BOTANY FOR BEGINNERS

CHAP.

connecting portion between the old plant and the new shoots is
destroyed, new plants are formed.

Leaves. — Cauline, alternate, simple, cordate, serrate ; the
small stipules fall off as the leaf expands.

Inflorescence. — The male flowers are arranged in a spike
known as a catkin (p. 170).

FIG. 266. — Hazel (Corylus). — i, Flowering branch ; 2, a male flower ; 3, a
4, a female flower ; 5 and 6, fruit ; 7, a foliage leaf. (S.)

stamen

The female flower appears as a small bud, recognised by the
coloured stigmas protruding from its apex.

Flower. — The male flower is incomplete, imperfect (p. 178),
and very minute.

The female flower is imperfect, incomplete, and minute.

xx THE CLASSIFICATION OF PLANTS 277

Perianth. — The male flower possesses no perianth ; the
stamens are fixed on a bract.

The female flower possesses a minute gamophyllous perianth
inserted on the ovary and therefore epigynous.

Androecium. — Male flower — free, 4, united to bract, each
anther is deeply lobed, so that there appear to be eight
stamens.

Gyncedum. — Female flower — syncarpous, carpels 2, inferior
style long, stigmas red ; the ovules develop after pollination.

Frtdt. -A nut.

Pollination. — The Hazel and its relations are pollinated by
the wind. That this may take place without difficulty the
flowers are produced before the foliage leaves. The Hazel
flowers in February, March, and early April.

Properties of Cupuliferae.— The bark of a few species of Oak, and
acorns, are used in medicine. The plants of the order are harmless, and
their properties are unimportant.

Economic importance of Cupuliferae. — This order is of great economic
value. The wood of the Oak is used very largely because of its hard-
ness, density, and durability. Its bark and acorn cupules are used for
tanning. Cork is also obtained from the Oak. The Beech produces
seeds— Beech Nuts— from which oil is obtained. The Hazel produces
nuts which are largely used for food. The seeds of the Chestnut
are edible, and form a most important article of food in die South of
Europe.

Class : MONOCOTYLEDONS.
Sub-class : Petaloidese.

Natural Order : Liliacese (Lily Family).— The plants of
this order are succulent herbs with perennial bulbs or rhizomes.
The leaves are generally long, narrow, and entire. The
inflorescence may be solitary or a raceme. The flowers are
large, actinomorphic and coloured. The perianth consists of
six leaves arranged in two series. The 6 stamens are arranged
in two series. The pistil is syncarpous, carpels 3, ovary
superior, style unbranched, stigmas 3-fid, ovules in axile
placentation. The fruit is a capsule.

Floral Formula.— [V $ + 3, A3 -f 3] 6(3).

Description of a Typical Flower of the Order
Liliacese. — (Hyacinthus Nonscriptus, Wild Hyacinth or
Bluebell.)

278

BOTANY FOR BEGINNERS

CHAP.

Habit.— A perennial herb with an underground bulb, narrow-
radical leaves, and a raceme of sweet-smelling blue flowers.

Q Root. — Adventitious roots are given off

from the lower surface of the bulb.
Stem. — An underground bulb (p. 23).
Leaves. —Radical, simple, narrow, entire,
green.

Inflorescence.— Indefinite, raceme.
Bracts. — Bracteate, blue, one at the base
of each pedicle.

Flower.- --Complete, actinomorphic. bell-
shaped, blue.

Perianth. — Gamophyllous (base only), 6
lobed, inferior.

Andracium. — Free, 6, in two series, epipetalous, filament
blue, anther 2-lobed, versatile.

FIG. 267.— Floral
diagram.

FIG. 268.— Flower of White Lily.

FIG. 269. — Longitudinal section of
flower of White Lily.

Gyncetium— Syncarpous, carpels 3, superior, style long,
stigma 3-fid, ovary 3-celled, ovules axile placentation.

THE CLASSIFICATION OF PLANTS

279

Fruit. — A capsule, seeds albuminous.

Pollination.— -The flowers may be pollinated by insects, or

Fie. 270. — Star of Bethlehem (Ornithogalum umbellatum). «, entire plant ; 3,
flower ; c, section of flower ; J, fruit ; e, section of fruit ; f, ovules and ovary. (S.)

self-pollination may take place. The stamens and pistil riper
at the same time.

280

BOTANY FOR BEGINNERS

CHAP.

EXCEPTIONS TO THE ABOVE TYPE.

This order is a very large one, and there are many species which
depart more or less from the above type.

Butcher's Broom (Rtiscus aculeatits}. — This is the only British
monocotyledonous shrub. Stem. — It grows in thickness by the produc-
tion of a new meristem layer in the cortex ; Leaves. — The leaves are
very minute, bearing in their axils leaf- like branches (cladodes) ;

FIG., 271.— Daffodil (Narcissus). A, leaves and flower; B, longitudinal section of
flower ; C, flower viewed from above ; D, transverse section of stem. (One-
fourth nat. size.)

Flowers. — The flowers are minute, and are produced on the face of
the cladode ; Stamens. — There are only 3 stamens, and the filaments
are united into a short stout column.

Herb-Paris (Paris quadrifolia). — This plant differs from monocoty-
ledonous plants in having the parts of the flower in fours, and its leaves
whorled. Perianth. — The perianth consists of 8 segments in 2 series,
but varies from 3 to 5 in each whorl ; Stamens. — There are usually
8 stamens, but these vary from 6 to 10 ; Pistil. — There are 4 carpels.

THE CLASSIFICATION OF PLANTS 281

Properties of Liliaceae. — Many of the plants in this order are poison-
ous, and a few are used in medicine. The principal poisonous plants
are —

Meadow Saffron (CW<72zV«;;/ autumnah}. — This plant possesses a sub-
terranean tuber, which gives rise to rose-coloured flowers, which appear
in August and September ; the fruit and leaves follow in spring. The
whole plant is poisonous, but the seeds and tubers contain the largest
quantity of the poisonous material.

Herb Paris \P. quadrifolid] and Lily of the Valley (Convallaria
majalis}) are also poisonous.

Tulip (Tulipa]. — The bulbs of the Tulip are poisonous, and also the
bulbs of Crown Imperial (Fritillaria imperialis}.

Natural Order : Amaryllideae (Daffodil Family).— These
plants have the same characters as the Liliaceae, with the excep-
tion of the pistil, which is inferior. Many of the members of
this order have a well developed corona, which is an outgrowth
of the perianth.

Floral formula.- [P(3 + 3) A3 + 3]G(5;.

Plants belonging to Amaryllidese.— The plants of this
order do not need any special description, they are so much
like the Liliacese in» every respect except the pistil. Well known
plants from among the Amaryllideas are the Daffodil or Lent
Lily (Narcissus Pseudo-narcissus}, and the Snow-drop
(Galanthus nivalis}, Snow-Flake (Leucojum cestwuni).

SUMMARY.

The Natural System of classification is based on the resemblances
and differences of plants.
Classification.—

THE PLANT KINGDOM.

I I

PHANEROGAMS CRPYTOGAMS

I I

Angiosperms Gymnosperms

Dicotyledons Monocotyledons

( including] ( including]

Each divided (Thalamiftorse Petaloicleoe ~\ Each divided into

into a I CalycifloKE Spadiciflorae j- a number of

number oj j Gamopetake Glumiflorae J Orders

Orders V Incomplete

282 BOTANY FOR BEGINNERS CHAP, xx

A natural order consists of a number of genera which possess some
common character.

A genus consists of one or more species which resemble one another
in one or more respects.

A species includes plants which must have descended from a common
ancestor.

QUESTIONS ON CHAPTER XIX AND XX.

(1) What are the chief distinctions between Monocotyledons and
Dicotyledons? (1898.)

(2) Describe and compare the corollas of any three of the following
plants, and mention the natural order to which each plant belongs —
Larkspur (Delphinium), Monkshood (Aconitum), Sweet Pea (Lalhy-
rus), Deadnettle (Lamium), Snapdragon (Antirrhinum). (1892.)

(3) Describe and compare the fruits of the Wallflower (Cheiranthus)
and the Pea (Pisum), and those of the Parsley (Petroselimini] and the
Dandelion (Taraxacum). To what natural orders do these plants re-
spectively belong ? ( 1 892. )

(4) Describe the general structure, position, and placentation of the
ovary in the Umbelliferoe, the Leguminosse, and the Labiate. (1891.)

(5) Describe the position, number, and arrangement of the stamens
in the flowers of the Cruciferce, the Composite, and the Primulacese.

(1891.)

(6) Give a general account of the structure of the flower of a Legu-
minous plant. (1899.)

(7) Describe carefully the structure of a leaf bud in any member of
the natural order Cupuliferoe. (1899.)

(8) Describe the arrangements of the stamens in the flowers of the
Buttercup, the Deadnettle, and the Sweet Pea. Refer these plants to
their natural orders. (1894.)

(9) Mention instances from the following natural orders of flowers, in
which the number of the stamens is (a) less than, or (b) greater than,
that of the petals, explaining in each case how the difference in
number arises — Ranunculaceas, Cruciferoe, Scrophularineae, Labiate.
(1890.)

(10) Describe with examples (a) a hypogynous, (b) a perigynous,
and (c) an epigynous flower. (1886.)

( 1 1 ) What is a placenta ? Describe the placentation in the Cruciferoe,
the Leguminosie, and the Liliaceoe. (1887.)

(12) How do the plants of the natural order Amaryllideoe differ from
those of the Liliaceae ?

CHAPTER XXI

PLANT DESCRIPTION

The Importance of Plant Description.— The impor-
tance of practical work in all branches of science is now uni-
versally admitted, and in Natural Science it is the only way to
obtain sound useful knowledge. In fact, this book is mainly
written for those persons who are willing to verify the principal
facts of botany by an appeal to Nature herself. Plant description
forms one of the most agreeable methods of approaching Nature.
The collection of plants (not with the idea of having so many
plants in a Herbarium), but to learn direct from Nature her
secrets, is always interesting. It is only by constant intercourse
with nature that true knowledge of living things can be obtained.
The able naturalist Goethe made the following remark : " Man
Sieht nur was man weiss," the trained naturalist goes about
and sees living things everywhere.

Apparatus Necessary for Plant Description.— The
apparatus necessary to examine the external parts of plants are
of the simplest description. These are shown below : —

(i) A sharp knife is necessary for making sections of stems,
flowers, buds, and ovaries. (2) Needles ; the three-sided glover's
needles are the best. These can be mounted in handles by forcing
the blunt end into fresh twigs ; when the twigs dry the needles
are held tight. These are used for separating the constituent
parts of small flowers, etc. (3) Pins are very useful for fixing
the parts of flowers on paper, cork, or wood in the form of a
diagram. (4) A hand-lens (p. 63). (5) A pah of forceps is
very useful for lifting small objects. (6) A book of forms1 for

1 Evans's forms for plant description are very useful.

284 BOTANY FOR BEGINNERS CHAP.

plant description is very useful, because it keeps the attention
of the student fixed on the most essential points. (7) A blank
drawing book and pencils will enable the student to make
sketches of the different parts of the plant.

How to Describe a Plant. --With a little practice a good
description of any ordinary plant should be made in about
three-quarters of an hour. Slovenliness should always be
avoided, and care must be taken to describe only those parts
which are present. To make certain that a good method of
work is ensured the following plan should be followed.

A PLAN FOR DESCRIBING PLANTS

(1) Habit. — Whether annual, biennial, or perennial; herbs, shrubs,
or trees (p. 19) ; size and general appearance.

(2) Boot. — Kind (p. 53). Whether a tap-root ; size, shape, and
branching, and adventitious, if present. Special roots, such as aerial.

(3) Stem. — (a) Kinds, such as herbaceous, or shrubby, or woody.

(b) Direction of growth — erect, creeping, underground, &c.

(d) Internal appearances — solid or hollow.

(e) Covering and colour— hairy or smooth, green, or other colour.

(4) Leaves. — (a) Kind of leaves — radical or cauline (p. 38).

(b) Phyllotaxis (p. 36)— alternate, opposite, whorled, or spiral
arrangement.

(c ) Simple or compound (p. 38).

(d) Composition of leaf — perfect, petiolate, sessile.

(e) Shape of leaf (p. 39).

(/) Vernation of leaf (p. 34).

(g) Colour and covering of leaf — hairy or smooth, dark or light green.

(h) Stipulate or exstipulate (p. 45).

(5) Inflorescence. — (a) Whether definite or indefinite (p. 166-172).
(b) Kind (p. 166-174).

(6) Bracts. — (a) Whether present or absent.
(b) Describe like foliage leaves.

(7) Flower.— (a) Whether complete or incomplete (p. 178).

(b) Whether actinomorphic or zygomorphic (p. 179).

(d} Diameter, colour, perfume.

(8) Calyx. — (a) Whether polysepalous or gamosepalous (p. 183).

(b) Number of sepals or lobes of calyx.

(9) Corolla. — (a) Whether polypetalous or gamopetalous.

(b) Number of petals or lobes of corolla.

(d) Shape of petals or lobes of corolla.

XXI

PLANT DESCRIPTION 285

Androecium. — (a) Whether free, monadelphous, diadelphous, or
polyadelphous (p. 185).

(b} Number of stamens or indefinite.

(d) Shape and length of filaments.

(e) Whether anther two-lobed, and how fixed to filaments, introrse
or extrorse.

Gynoecium. — (a) Whether monocarpous, apocarpous, or syncarpous
(p. 186).

(b) Number of carpels.

(e) Whether stigmas terminal, 2-fid, 3-fid, 4-fid, &c.
(/) Whether ovary one, two, three, or more celled.
Ovules. — (a) How many.

(b} Placentation — axile, parietal, free-central, or basal (p. 187).
Floral Formula (p. 188).
Floral Diagram (p. 188).

Classification. — Place the plant in its true position in the natural
system, as follows : —

Sub- Kingdom . ~\

oT". : : : k 245>-

Sub-Class. . . J

Natural Order.

Genus.

Species. [If possible name the plant.]

Common Name.

EXAMPLE OF PLANT DESCRIPTION

Habit. — An erect perennial herb, with radical leaves, growing
in damp ditches or marshy places.

Root. — Absent.

Stem. — Herbaceous, erect, ribbed, twisted, solid, hairy,
brownish purple.

Leaves. — Radical leaves crowded, petiolate, pinnate, reticu-
late-veined, cauline leaves alternate, compound, ternate ; the
terminal leaflet large, upper part of leaflet crenate, hairy, upper
side dark green and under side light green, stipulate, stipules
adnate, small and lobed.

Inflorescence.— Definite, two-flowered cyme, drooping.

Flower.— Complete, actinomorphic, roughly campanulate, £
of an inch in diameter, honeyed, dull orange, protandrous.

286 BOTANY FOR BEGINNERS CHAP, xxi

Calyx. — Gamosepalous, 10 lobes, 5 alternating, lobes small,
inferior, lobes toothed, hairy, reddish brown.

Corolla.— Polypetalous, 5lobed,perigynous, petals triangular
in shape, veined, alternating with lobes of calyx.

Androecium (Stamens). — Free, indefinite, perigynous, fila-
ments short, anthers 2 lobed and versatile, introrse, the outer
whorl ripening first.

Gyncecium (Pistil). — Apocarpous,carpels numerous,superior,
styles long, filiform, stigmas terminal and coloured.

Ovules. — One ovule in each carpel, placentation basal.

Fruit. — Not developed.

Floral formula.— [K (5) c 5, A QQ ] G QQ .

Floral Diagram.— (p. 258.)

CLASSIFICATION

Sub-Kingdom : Phanerogams. I place this plant in the
above sub-kingdom because it is a flowering plant.

Division : Angiosperms. I place the plant in this division
because the ovules are enclosed in carpels.

Class : Dicotyledons. I place this plant in the above Class
because the leaves are reticulate-veined, and the parts of the
flower are in fives.

Sub-Class: Calyciflorse. This plant belongs to this sub-class
because the petals and stamens are inserted on the calyx
and are perigynous.

Natural Order : Eosaceae. This plant belongs to this natural
order, because of the indefinite stamens (which are perigynous),
and its apocarpous pistil; the perigynous stamens distinguish it
from a Ranunculus.

Genera : Geum.

Species : Rivale.

Common Name : Water Aven.

For other examples see Chapters on Classification.

INDEX

ABSORPTION, by roots, 137 — : Blackberry, 260 Cherry, 260

140 ; Blade, 34 Chicory, 268

Absorption of gases, 121 Bladderwort, 131 Chlorine, 117

Acacia, 42 Bleeding, 145 Chlorophyll, 8t

Achene. 228

Borage, 270 Chloroplast, 81, 84

Acicular, 39

Boragineae, 270 Chromoplast, 84, 86

Actinomorphic, 179

Bordered pits, 78 Circulation of protoplasm, 8c

Adhesion, 182

Botany, i Classification, 3, 4, 242

Adventitious, 25, 53

Branches, 9 ; formation of, 113 Cleistogamic, 216

Aerial roots, 54

Bugloss, 271

Clematis, 248

,, stems, 8
Air bubbles, 63

Bulbs, 23
Bundles, 66, 98

Climbing plants, 25 — 28
Closed bundles, 98

Air chamber, 112

Butcher's broom, 280

Closing of flowers, 160

Albuminous, 219

Buttercup, 246 | Closing membrane, 77

Alchemilla, 261

Butterwort, 130

Clover, 133

Aleurone grains, 86
Amaryllideae, 281

CALCIUM, 117

Cohesion, 182
Colour of flowers, 182

Anatomy, 4, 16

Callus, Q7

Combustible elements, 117

Anatropous, 203 Caltha, '248

Comfrey, 271

Androecium, 164, 184 ; struc- Calyciflorae, 243, 254

Common bundles, 100

ture of, 196 Calyx, 164, 183

Companion cells, 93

Anemone, 248 Cambium, 98, 99, 105 ; inter- Complete flower, 178

Anemophilous, 207 fascicular, 104 ; ring, 104 | Compositae, 265

Angiosperms, 242, 243

Campanulate, 181

Compound leaves, 38, 40

Annual, 19 ; rings, 68, 107

Campion, 253

Convolute, 48

Anterior, 180
Anther, 186 ; structure of, 197

Campylotropous, 203
Candy tuft, 168

Convolvulus, 181
Cordate, 39

Apocarpous, 186

Cane sugar, 88

Cork, 67 ; cambium, 107

Apple, 261

Capitulum, 168

Corm, 23

Aquilegia, 248

Capsule, 229

Corolla, 164, 184

Aril, 223

Carbohydrates, 76

Corona, 281

Arum, 170

Carbon, 117, 120

Cortex, 66, 101

Ash, 117

Carbonaceous food. See car-

Corylus, 275

Assimilation, 121

bon 1 Corymb, 168,

Axil of leaf, 9

Carbon dioxide, i 9, 121, 123 ! Cotyledons, n

Axillary, 166 i Carnivorous plants, 128 — 132
Axis, 8; descending, 51 Carpel, 165

Creeping-stem, 8
Cruciferae, 249

Carrot, 56

Crystal, 2, 81

BACTERIA, 132
Barberry, 146

Caryophylleae, 2^2
Catkin, 170

Crystalloid, 86
Cupuliferae, 275

Bark, 107 — 108

Cauline bundles, 100 ! Cuticle, 77

Basal placentation, 187 j Cell, 65, 74 ; contents of, 81 ; Cutin, 76

Basifixed, 186

kinds of, 92 ; mature, 81 ;

Bast, 99, 100

structure of 74 ; young, 81

Bean, 10

Cell-sap, 8 1, 82

DAFFODIL, 281

Beech, 17

Cellulose, 76

Dahlia, 146

Bellis, 265 Cell-wall, 65, 74 ; chemical

Daisy, 265

Berry, 228 changes in, 76; composition
Biennial, 19 i of, 75

Dandelion, 266
Daughter-cell, 89, 198

288

INDEX

Deadnettle, 274

Fruits, 224 ; classification of,

Interfascicular cambium. 104

Delphinium, 248

227 ; kinds of, 224 Internode, 19

Dermatogen, 112

Functions, 116 Intine, 199

Description of plants, 283

Funiculus, 201, 223 Introrse, 186

Diadelphous, 185

Fusiform, 57 Intussusception, 75

Diastase, 122

Involucre, 175

Dichotomous, 172

GAMOPETAL^E, 243, 265 Iodine solution, 75

Dicotyledon, 12, 68, 224

Gamophyllous, 188 ; Irregular, 178

Didynamous, 185

Genus, 245 | Irritability, 155 ; of growing

Digitalis, 272

Geotropism, 158-159 organs, 156 ; of mature

Dimorphic, 209

Germination, 12

organs, 160

Dodder, 129

Glabrous (see smooth)

Dorsal. See posterior
Dorsifixed, 186
Drupe, 227
Druplet, 228
Dry substance of plants, 117

EBRACTEATE, 46

Glands, 96
Glandular hairs, 96
Globoid, 86
Glomerule, 174
Gorse, 180
Growing point of root, 113 ;
of stem, 108

LABIATE, 182
Labiateae, 274
Ladies' mantle, 261
Lamina. See. blade
Lanceolate, 39
Larkspur, 248
Leaf structures, 8 ; apex of,

Egg-apparatus, 201
Elaborated sap, 148
Elements of plant food, n8 ;
essential, 118; non-essential,

134
Elm, 18
Embryo, n, 12, 217 j sac, 201
Emergencies, 30, 96

Growth, 152
Growth by appositi6n, 75 ; by-
intussusception, 75
Guard-cells, 94
Gynandrous, 185
Gynoecium, 165, 186, 201
Gynobasic, 186
Gymnosperms, 242

43 ; climbers, 26 ; margin
of, 42 ; perfect, 34 ; reticu-
late and parallel, 34 ; scar,
67
Leaves, 31 ; bracteate, 31, 46 ;
floral, 31, 47, 164 ; foliage,
31 ; formation of, 113 ; op-
posite, 37 ; radical, 38 ;

Endocarp, 225

HABIT 284 shapes, 39-42

Endodermis, 103, 105

Hairs of Legume, 229

Endosperm, 12, 219
Entomophilous, 207
Epicalyx, 260
Epicarp, 225

n.airs, 95
Hand-lens, 63, 64
Hard bast, 99, 100
Harebell, 181

Legummosae, 254
Leguminose plant, 132
Lenticel, 108, 142, 143
Lettuce, 268

Epidermis, 94
Epigynous, 185
Epipetalous, 185
Epiphyllous, 188
Epiphyte, 54
Essential organs, 196
Extine, 199
Extrorse, 186

Hazel, 275
Head, 168
Heat due to respiration, 125
Helianthus, 268
Heliotropism, 156 — 158
Helleborus, 248
Herbaceous, 19
Herb Paris, 280
Heterostyled, 209
Histology, 4 ; of the cell, 74 —

Leucoplast, 8r, 82, 84, 85
Life-history, 5, 239
Light, 122, 153
Lignification, 77
Ligulate, 181
Liguliflorae, 266
Lilac, 47
Lmaceae, 277
Lily of the valley, 281

T imo l\8

FATS, 81, 87

91 ; of the tissues, 92-102 ; ! J o'nX}t^dinal section 6l

Female flower, 179

of the shoot and root, 102—

Ferment, 122

JI5

Fertilisation, 216 ; results of,

Hook-climbers, 25

MAGNESIUM, 117, 134

220

Fibrous roots, 53

Hop, 26 Maize, 68
House-leek, 20 j Male flower, 178

Filament, 186

How to describe a plant, 284 Marsh marigold, 248

Floral diagram, 188

Humble-bee flowers, 214

Median plane, 180

,, formulae, 188

Hyacinth, no

Medullary rays, 104

,, leaves, 164

Hydrogen, 117

Members, 8

Flowering plants, 206

Hypogynous, 185

Meristem, 99

Flower, 178

Mesocarp, 225

Foliage leaves, 34

IMBRICATED, 175 Mesophyll, in

Follicle, 230

Incompletae, 243, 275

Micropyle, 10

Food of plants, 120
Fool's parsley, 264

Incomplete flowers, 178 Microscope, 71, 72
Indehiscent, 228 : Mid-rib of leaf, 35

Forget-me-not, 270 Inferior. 181

Mineral salts, 134

Foxglove, 272

Inflorescence, 166

Monadelphous, 185

Free-cell formation, 90 Integuments, 201

Monkshood, 248

Free-central placentation, 187 1 Intercellular spaces, ni

Monocarpous, 186

INDEX

289

Monocotyledon, 12, 242; stem,
109 ; root, no

Petaloid, 188
Petaloideae, 243. 277

RACEME, 167
Radial longitudinal section,

Monoecious, 208

Petiolate, 34

Morphology, 3, 4, 8—15
Mother pollen cell, 198
Mounting specimens. 62

Phanerogam, 242
Phelloderm, 107, 108
Phellogen, 107, 108

Radical leaves, 38
Radicle, n
Ranunculaceae, 246

Movements of protoplasm, 79
Mustard seeds, 12, 52

Phloem, 98, 99, 100
Phosphorus, 117, 132

Ranunculus, 246
Raphides, 87

Phyllotaxis, 36—38

Raspberry, 260

NAMING of plants, 245
Napiform, 57
Natural history, 5
Natural system, 5
Nectary, 207

Physiology, 4 ; of movement,
4, 152 — 163 ; of nutrition, 4,
116 — 136; of reproduction,
4, 235—241
Pine, 70
Pinnate, 41

Receptacle, 178
Regular, 178-179
Reniform, 39
Reproduction, 89, 237-238
Reserve material, 12
Respiration, 124-128

jsj ettle, 90
Net-veined. See reticulate
Nitragin, 133

Pistil, 165
Pitcher plant, 132
Pitted vessel, 93

Resting or dormant buds, 17
Reticulate leaves, 34
Rhizome, 21, 22

^Nitrates, 128
Nitrogen, 117, 128
Node 19

Placenta, 187
Placentation, 187 ; kinds of,

Roots, adventitious, 14, 53 ;
aerial, 54 ; clinging, 53 ;

Non-essential organs, 196
Nucellus 201

107
Plant description, 283

conical, 57 ; fusiform ; 57
movements of, 58 ; uses of,

Nucleolus, 8 1
Nucleus, 8 1

Plantain, 166
Plasmolysis, 81
Plerome, 112

58
Root-cap, 113, 52
Root-climbers, 53

x u n , no

Plumule, n

Root-hair's, 52, 95, 137

Pod. See legume

Root-pressure, 145-146

OAK, 17, 147
Obovate, 39

Pollen grain, 164 ; develop-
ment of, 199 ; structure of,

Rosaceae, 257
Rose, 2<;7

Offset, 20

198 ' Rotation of protoplasm, Bo

Onion, 23

Pollen sac, 197 j Rubus, 260

Oosphere, 201

Pollen tube 217

Oospore, 217

Pollination, 206 — 207

Open bundle, 98
Opening of flowers, 160 — 161

Polyadelphous, 185
Polypetalous, 184

SACCATE, 190, 251
Sagittate, 39

Order, 245
Osmosis, 139

Polyphyllous, 188
Polysepalous, 183

Saprophyte, 123
Scale leaves, 46

Ovary, 165
Ovule, 165 ; development of

Pome, 227
Pojppy, 226

Scarlet runner, 26
Schulze's solution, 88

202 ; kinds of, 203

Posterior, 180

Sclerenchyma, 104, 105

Oxygen, 117, 126

Potassium, 107, 134

Scorpioid, 173

Prickles, 30

Scrophularineae, 271

PALISADE TISSUE, in

Primrose, 268

Secondary growth, 106

Palmate, 43

Primulaceae, 268

Sections, how to prepare, 61-

Panicle, 168

Prcefoliation, 47

Papilionaceous, 181

Properties of Boragineae, 270 ;

Seeds, examples of, ,223 ; dis-

Pappus, 184

of Caryophylleae, 253 ; of

tribution of, 231 ; germina-

Parasites, 24, 123

Cruciferae, 251 ; of Com-

tion of, 234

Parenchyma, 92
Parietal placentation, 187

positae, 267 ; of Cupuliferae,
277 ; of Labiatae, 275 ; of

Seedlings, 13-14
Self-fertilisation, 215

Peach, 227

Leguminosae, 256 ; of Lili-

Sepal, 164, 183, 194

Pear, 261

aceae, 281 ; of Primulaceae,

Serrated, 42

Pedicel, 166

269 ; of Ranunculaceae, 248,

Shepherd's purse, 217, 218

Peduncle, 166

of Rosaceae, 262 ; of Scro- Shoot, 16-50

Perennial, 19

phularineas, 273 ; of Umbel- i Shrub, 20

Perfect flower, 178

liferae, 264 ! Sieve-plate, 93

Perianth, 187

Proteids, 79

Sieve-tube, 93

Periblem, 112

Protandrous, 208

Silica. See silicon, 117, 135

Pericycle, 103, 105

Protogynous, 209

Silicula, 229

Periderm, 107, 108

Protoplasm, 79 — 80

Silqua, 229

Perigynous, 184, 185

Prunus, 260

Sleep of plants, 160-161

Perisperm, 220, 223

Pseudocarp, 224

Smooth, 29

Personate, 182

Pulmonaria, 271

Sodium, 117, 135,

Petal, 164

Pyrus, 261

Solomon's seal, 22

290

INDEX

Spadici florae, 243

Superior, 183

Spadix, 170

Symbiosis, 133

Spathe, 170

Syncarpous, 186

Spatulate, 39

Syngenesious, 185

Species, 245

Spectrum, 122 1 TANGENTIAL sections, 61,62

Speedwell, 273 ! Taproot, 52

Spermoderm, n j Taraxacum, 266

Spike, 1 66

Tegmen, n

Spine, 30

Tendril, 27

Spiral vessel, 93

Testa, ii

Spongy parenchyma, in Tetradynamous, 185

Spotted orchis, 212

Thalamiflorae, 242. 246

Spurious fruit, 224 i Thalamus. See torus

Spurred flower, 181 j Thorn, 30

Stamen, 184, 196

Tillering, 17

Starch, 85

Tissue, 6C

Stigma, 1 86

Tissues, epidermal, 65, 94 ;

Stinging nettle, 96

vascular, 65, 94, 98; ground,

Stipulate, 256
Stipule, 45

66, 94, 101
Tormentilla, 245

Stitchwort, 252

Torus, 178^

St. John's wort, 185
Stolon, 21

Transpiration, 140 — 147
Transverse plane of flower,

Stomata, 94, 142

,80

Strawberry, 260
Structure of dicotyledonous

Transverse sections, 61, 62
Traveller's joy, 248

stem, 102, 103

Tree, 20

Style, 186 ' Trimorphic, 211

Subterranean stems, 8, 21 Tuber, 22

Succulent fruits, 227

Tubercular root, 57

Sucker, 21

Tubular flowers, 181

Sugars, 88
Sulphur, 117

Tubuliflorae, 265
Tulipa, 281

Sundew, 128

Turnip, 57

Sunflower, 66, 68, 268

Twining stems, 26

UMBLE, compound, 168 ; sim-
ple, 168

Umbelliferae, 262
' Unicellular hairs, 95
I Unicostate, 35

VACUOLES, 81
Vascular bundles, ico
Vascular cylinder, 69
Vegetable marrow, 69
Venation, 34
Venus's fly-trap, 132
Vernation, 47
Veronica, 273
Versatile, 186
Verticillaster, 173
Vessels, kinds of, 93
Vine, 145
Violet, explosive fruits of, 233

WALLFLOWER, 250
Water culture, 118, 119; so-
lution for, 118
Water dropwort, 264
Water hemlock, 264
Water pore, 95, 145
White light, composition of

Whorled leaves. See phyllo-

taxis

Wild hyacinth, 277
Willows, 233
Wood sorrel, 233

XYLEM, 98, 100
ZYGOMORPHIC, 179

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